Archive for the 'temporary equilibrium' Category

Roger Farmer’s Prosperity for All

I have just read a review copy of Roger Farmer’s new book Prosperity for All, which distills many of Roger’s very interesting ideas into a form which, though readable, is still challenging — at least, it was for me. There is a lot that I like and agree with in Roger’s book, and the fact that he is a UCLA economist, though he came to UCLA after my departure, is certainly a point in his favor. So I will begin by mentioning some of the things that I really liked about Roger’s book.

What I like most is that he recognizes that beliefs are fundamental, which is almost exactly what I meant when I wrote this post (“Expectations Are Fundamental”) five years ago. The point I wanted to make is that the idea that there is some fundamental existential reality that economic agents try — and, if they are rational, will — perceive is a gross and misleading oversimplification, because expectations themselves are part of reality. In a world in which expectations are fundamental, the Keynesian beauty-contest theory of expectations and stock prices (described in chapter 12 of The General Theory) is not absurd as it is widely considered to be believers in the efficient market hypothesis. The almost universal unprofitability of simple trading rules or algorithms is not inconsistent with a market process in which the causality between prices and expectations goes in both directions, in which case anticipating expectations is no less rational than anticipating future cash flows.

One of the treats of reading this book is Farmer’s recollections of his time as a graduate student at Penn in the early 1980s when David Cass, Karl Shell, and Costas Azariadis were developing their theory of sunspot equilibrium in which expectations are self-fulfilling, an idea skillfully deployed by Roger to revise the basic New Keynesian model and re-orient it along a very different path from the standard New Keynesian one. I am sympathetic to that reorientation, and the main reason for that re-orientation is that Roger rejects the idea that there is a unique equilibrium to which the economy automatically reverts, albeit somewhat more slowly than if speeded along by the appropriate monetary policy, on its own. The notion that there is a unique equilibrium to which the economy automatically reverts is an assumption with no basis in theory or experience. The most that the natural-rate hypothesis can tell us is that if an economy is operating at its natural rate of unemployment, monetary expansion cannot permanently reduce the rate of unemployment below that natural rate. Eventually — once economic agents come to expect that the monetary expansion and the correspondingly higher rate of inflation will be maintained indefinitely — the unemployment rate must revert to the natural rate. But the natural-rate hypothesis does not tell us that monetary expansion cannot reduce unemployment when the actual unemployment rate exceeds the natural rate, although it is often misinterpreted as making that assertion.

In his book, Roger takes the anti-natural-rate argument a step further, asserting that the natural rate of unemployment rate is not unique. There is actually a range of unemployment rates at which the economy can permanently remain; which of those alternative natural rates the economy winds up at depends on the expectations held by the public about nominal future income. The higher expected future income, the greater consumption spending and, consequently, the greater employment. Things are a bit more complicated than I have just described them, because Roger also believes that consumption depends not on current income but on wealth. However, in the very simplified model with which Roger operates, wealth depends on expectations about future income. The more optimistic people are about their income-earning opportunities, the higher asset values; the higher asset values, the wealthier the public, and the greater consumption spending. The relationship between current income and expected future income is what Roger calls the belief function.

Thus, Roger juxtaposes a simple New Keynesian model against his own monetary model. The New Keynesian model consists of 1) an investment equals saving equilibrium condition (IS curve) describing the optimal consumption/savings decision of the representative individual as a locus of combinations of expected real interest rates and real income, based on the assumed rate of time preference of the representative individual, expected future income, and expected future inflation; 2) a Taylor rule describing how the monetary authority sets its nominal interest rate as a function of inflation and the output gap and its target (natural) nominal interest rate; 3) a short-run Phillips Curve that expresses actual inflation as a function of expected future inflation and the output gap. The three basic equations allow three endogenous variables, inflation, real income and the nominal rate of interest to be determined. The IS curve represents equilibrium combinations of real income and real interest rates; the Taylor rule determines a nominal interest rate; given the nominal rate determined by the Taylor rule, the IS curve can be redrawn to represent equilibrium combinations of real income and inflation. The intersection of the redrawn IS curve with the Phillips curve determines the inflation rate and real income.

Roger doesn’t like the New Keynesian model because he rejects the notion of a unique equilibrium with a unique natural rate of unemployment, a notion that I have argued is theoretically unfounded. Roger dismisses the natural-rate hypothesis on empirical grounds, the frequent observations of persistently high rates of unemployment being inconsistent with the idea that there are economic forces causing unemployment to revert back to the natural rate. Two responses to this empirical anomaly are possible: 1) the natural rate of unemployment is unstable, so that the observed persistence of high unemployment reflect increases in the underlying but unobservable natural rate of unemployment; 2) the adverse economic shocks that produce high unemployment are persistent, with unemployment returning to a natural level only after the adverse shocks have ceased. In the absence of independent empirical tests of the hypothesis that the natural rate of unemployment has changed, or of the hypothesis that adverse shocks causing unemployment to rise above the natural rate are persistent, neither of these responses is plausible, much less persuasive.

So Roger recasts the basic New Keynesian model in a very different form. While maintaining the Taylor Rule, he rewrites the IS curve so that it describes a relationship between the nominal interest rate and the expected growth of nominal income given the assumed rate of time preference, and in place of the Phillips Curve, he substitutes his belief function, which says that the expected growth of nominal income in the next period equals the current rate of growth. The IS curve and the Taylor Rule provide two steady state equations in three variables, nominal income growth, nominal interest rate and inflation, so that the rate of inflation is left undetermined. Once the belief function specifies the expected rate of growth of nominal income, the nominal interest rate consistent with expected nominal-income growth is determined. Since the belief function tells us only that the expected nominal-income growth equals the current rate of nominal-income growth, any change in nominal-income growth persists into the next period.

At any rate, Roger’s policy proposal is not to change the interest-rate rule followed by the monetary authority, but to propose a rule whereby the monetary authority influences the public’s expectations of nominal-income growth. The greater expected nominal-income growth, the greater wealth, and the greater consumption expenditures. The greater consumption expenditures, the greater income and employment. Expectations are self-fulfilling. Roger therefore advocates a policy by which the government buys and sells a stock-market index fund in order to keep overall wealth at a level that will generate enough consumption expenditures to support maximum sustainable employment.

This is a quick summary of some of the main substantive arguments that Roger makes in his book, and I hope that I have not misrepresented them too badly. As I have already said, I very much sympathize with his criticism of the New Keynesian model, and I agree with nearly all of his criticisms. I also agree wholeheartedly with his emphasis on the importance of expectations and on self-fulfilling character of expectations. Nevertheless, I have to admit that I have trouble taking Roger’s own monetary model and his policy proposal for stabilizing a broad index of equity prices over time seriously. And the reason I am so skeptical about Roger’s model and his policy recommendation is that his model, which does after all bear at least a family resemblance to the simple New Keynesian model, strikes me as being far too simplified to be credible as a representation of a real-world economy. His model, like the New Keynesian model, is an intertemporal model with neither money nor real capital, and the idea that there is an interest rate in such model is, though theoretically defensible, not very plausible. There may be a sequence of periods in such a model in which some form of intertemporal exchange takes place, but without explicitly introducing at least one good that is carried over from period to period, the extent of intertemporal trading is limited and devoid of the arbitrage constraints inherent in a system in which real assets are held from one period to the next.

So I am very skeptical about any macroeconomic model with no market for real assets so that the interest rate interacts with asset values and expected future prices in such a way that the existing stock of durable assets is willingly held over time. The simple New Keynesian model in which there is no money and no durable assets, but simply bonds whose existence is difficult to rationalize in the absence of money or durable assets, does not strike me as a sound foundation for making macroeconomic policy. An interest rate may exist in such a model, but such a model strikes me as woefully inadequate for macroeconomic policy analysis. And although Roger has certainly offered some interesting improvements on the simple New Keynesian model, I would not be willing to rely on Roger’s monetary model for the sweeping policy and institutional recommendations that he proposes, especially his proposal for stabilizing the long-run growth path of a broad index of stock prices.

This is an important point, so I will try to restate it within a wider context. Modern macroeconomics, of which Roger’s model is one of the more interesting examples, flatters itself by claiming to be grounded in the secure microfoundations of the Arrow-Debreu-McKenzie general equilibrium model. But the great achievement of the ADM model was to show the logical possibility of an equilibrium of the independently formulated, optimizing plans of an unlimited number of economic agents producing and trading an unlimited number of commodities over an unlimited number of time periods.

To prove the mutual consistency of such a decentralized decision-making process coordinated by a system of equilibrium prices was a remarkable intellectual achievement. Modern macroeconomics deceptively trades on the prestige of this achievement in claiming to be founded on the ADM general-equilibrium model; the claim is at best misleading, because modern macroeconomics collapses the multiplicity of goods, services, and assets into a single non-durable commodity, so that the only relevant plan the agents in the modern macromodel are called upon to make is a decision about how much to spend in the current period given a shared utility function and a shared production technology for the single output. In the process, all the hard work performed by the ADM general-equilibrium model in explaining how a system of competitive prices could achieve an equilibrium of the complex independent — but interdependent — intertemporal plans of a multitude of decision-makers is effectively discarded and disregarded.

This approach to macroeconomics is not microfounded, but its opposite. The approach relies on the assumption that all but a very small set of microeconomic issues are irrelevant to macroeconomics. Now it is legitimate for macroeconomics to disregard many microeconomic issues, but the assumption that there is continuous microeconomic coordination, apart from the handful of potential imperfections on which modern macroeconomics chooses to focus is not legitimate. In particular, to collapse the entire economy into a single output, implies that all the separate markets encompassed by an actual economy are in equilibrium and that the equilibrium is maintained over time. For that equilibrium to be maintained over time, agents must formulate correct expectations of all the individual relative prices that prevail in those markets over time. The ADM model sidestepped that expectational problem by assuming that a full set of current and forward markets exists in the initial period and that all the agents participating in the economy are present and endowed with wealth enabling them to trade in the initial period. Under those rather demanding assumptions, if an equilibrium price vector covering all current and future markets is arrived at, the optimizing agents will formulate a set of mutually consistent optimal plans conditional on that vector of equilibrium prices so that all the optimal plans can and will be carried out as time happily unfolds for as long as the agents continue in their blissful existence.

However, without a complete set of current and forward markets, achieving the full equilibrium of the ADM model requires that agents formulate consistent expectations of the future prices that will be realized only over the course of time not in the initial period. Roy Radner, who extended the ADM model to accommodate the case of incomplete markets, called such a sequential equilibrium, an equilibrium of plans, prices and expectations. The sequential equilibrium described by Radner has the property that expectations are rational, but the assumption of rational expectations for all future prices over a sequence of future time periods is so unbelievably outlandish as an approximation to reality — sort of like the assumption that it could be 76 degrees fahrenheit in Washington DC in February — that to build that assumption into a macroeconomic model is an absurdity of mind-boggling proportions. But that is precisely what modern macroeconomics, in both its Real Business Cycle and New Keynesian incarnations, has done.

If instead of the sequential equilibrium of plans, prices and expectations, one tries to model an economy in which the price expectations of agents can be inconsistent, while prices adjust within any period to clear markets – the method of temporary equilibrium first described by Hicks in Value and Capital – one can begin to develop a richer conception of how a macroeconomic system can be subject to the financial disturbances, and financial crises to which modern macroeconomies are occasionally, if not routinely, vulnerable. But that would require a reorientation, if not a repudiation, of the path on which macroeconomics has been resolutely marching for nigh on forty years. In his 1984 paper “Consistent Temporary Equilibrium,” published in a volume edited by J. P. Fitoussi, C. J. Bliss made a start on developing such a macroeconomic theory.

There are few economists better equipped than Roger Farmer to lead macroeconomics onto a new and more productive path. He has not done so in this book, but I am hoping that, in his next one, he will.

Price Stickiness Is a Symptom not a Cause

In my recent post about Nick Rowe and the law of reflux, I mentioned in passing that I might write a post soon about price stickiness. The reason that I thought it would be worthwhile writing again about price stickiness (which I have written about before here and here), because Nick, following a broad consensus among economists, identifies price stickiness as a critical cause of fluctuations in employment and income. Here’s how Nick phrased it:

An excess demand for land is observed in the land market. An excess demand for bonds is observed in the bond market. An excess demand for equities is observed in the equity market. An excess demand for money is observed in any market. If some prices adjust quickly enough to clear their market, but other prices are sticky so their markets don’t always clear, we may observe an excess demand for money as an excess supply of goods in those sticky-price markets, but the prices in flexible-price markets will still be affected by the excess demand for money.

Then a bit later, Nick continues:

If individuals want to save in the form of money, they won’t collectively be able to if the stock of money does not increase.There will be an excess demand for money in all the money markets, except those where the price of the non-money thing in that market is flexible and adjusts to clear that market. In the sticky-price markets there will nothing an individual can do if he wants to buy more money but nobody else wants to sell more. But in those same sticky-price markets any individual can always sell less money, regardless of what any other individual wants to do. Nobody can stop you selling less money, if that’s what you want to do.

Unable to increase the flow of money into their portfolios, each individual reduces the flow of money out of his portfolio. Demand falls in stick-price markets, quantity traded is determined by the short side of the market (Q=min{Qd,Qs}), so trade falls, and some traders that would be mutually advantageous in a barter or Walrasian economy even at those sticky prices don’t get made, and there’s a recession. Since money is used for trade, the demand for money depends on the volume of trade. When trade falls the flow of money falls too, and the stock demand for money falls, until the representative individual chooses a flow of money out of his portfolio equal to the flow in. He wants to increase the flow in, but cannot, since other individuals don’t want to increase their flows out.

The role of price stickiness or price rigidity in accounting for involuntary unemployment is an old and complicated story. If you go back and read what economists before Keynes had to say about the Great Depression, you will find that there was considerable agreement that, in principle, if workers were willing to accept a large enough cut in their wages, they could all get reemployed. That was a proposition accepted by Hawtry and by Keynes. However, they did not believe that wage cutting was a good way of restoring full employment, because the process of wage cutting would be brutal economically and divisive – even self-destructive – politically. So they favored a policy of reflation that would facilitate and hasten the process of recovery. However, there also those economists, e.g., Ludwig von Mises and the young Lionel Robbins in his book The Great Depression, (which he had the good sense to disavow later in life) who attributed high unemployment to an unwillingness of workers and labor unions to accept wage cuts and to various other legal barriers preventing the price mechanism from operating to restore equilibrium in the normal way that prices adjust to equate the amount demanded with the amount supplied in each and every single market.

But in the General Theory, Keynes argued that if you believed in the standard story told by microeconomics about how prices constantly adjust to equate demand and supply and maintain equilibrium, then maybe you should be consistent and follow the Mises/Robbins story and just wait for the price mechanism to perform its magic, rather than support counter-cyclical monetary and fiscal policies. So Keynes then argued that there is actually something wrong with the standard microeconomic story; price adjustments can’t ensure that overall economic equilibrium is restored, because the level of employment depends on aggregate demand, and if aggregate demand is insufficient, wage cutting won’t increase – and, more likely, would reduce — aggregate demand, so that no amount of wage-cutting would succeed in reducing unemployment.

To those upholding the idea that the price system is a stable self-regulating system or process for coordinating a decentralized market economy, in other words to those upholding microeconomic orthodoxy as developed in any of the various strands of the neoclassical paradigm, Keynes’s argument was deeply disturbing and subversive.

In one of the first of his many important publications, “Liquidity Preference and the Theory of Money and Interest,” Franco Modigliani argued that, despite Keynes’s attempt to prove that unemployment could persist even if prices and wages were perfectly flexible, the assumption of wage rigidity was in fact essential to arrive at Keynes’s result that there could be an equilibrium with involuntary unemployment. Modigliani did so by positing a model in which the supply of labor is a function of real wages. It was not hard for Modigliani to show that in such a model an equilibrium with unemployment required a rigid real wage.

Modigliani was not in favor of relying on price flexibility instead of counter-cyclical policy to solve the problem of involuntary unemployment; he just argued that the rationale for such policies had to be that prices and wages were not adjusting immediately to clear markets. But the inference that Modigliani drew from that analysis — that price flexibility would lead to an equilibrium with full employment — was not valid, there being no guarantee that price adjustments would necessarily lead to equilibrium, unless all prices and wages instantaneously adjusted to their new equilibrium in response to any deviation from a pre-existing equilibrium.

All the theory of general equilibrium tells us is that if all trading takes place at the equilibrium set of prices, the economy will be in equilibrium as long as the underlying “fundamentals” of the economy do not change. But in a decentralized economy, no one knows what the equilibrium prices are, and the equilibrium price in each market depends in principle on what the equilibrium prices are in every other market. So unless the price in every market is an equilibrium price, none of the markets is necessarily in equilibrium.

Now it may well be that if all prices are close to equilibrium, the small changes will keep moving the economy closer and closer to equilibrium, so that the adjustment process will converge. But that is just conjecture, there is no proof showing the conditions under which a simple rule that says raise the price in any market with an excess demand and decrease the price in any market with an excess supply will in fact lead to the convergence of the whole system to equilibrium. Even in a Walrasian tatonnement system, in which no trading at disequilibrium prices is allowed, there is no proof that the adjustment process will eventually lead to the discovery of the equilibrium price vector. If trading at disequilibrium prices is allowed, tatonnement is hopeless.

So the real problem is not that prices are sticky but that trading takes place at disequilibrium prices and there is no mechanism by which to discover what the equilibrium prices are. Modern macroeconomics solves this problem, in its characteristic fashion, by assuming it away by insisting that expectations are “rational.”

Economists have allowed themselves to make this absurd assumption because they are in the habit of thinking that the simple rule of raising price when there is an excess demand and reducing the price when there is an excess supply inevitably causes convergence to equilibrium. This habitual way of thinking has been inculcated in economists by the intense, and largely beneficial, training they have been subjected to in Marshallian partial-equilibrium analysis, which is built on the assumption that every market can be analyzed in isolation from every other market. But that analytic approach can only be justified under a very restrictive set of assumptions. In particular it is assumed that any single market under consideration is small relative to the whole economy, so that its repercussions on other markets can be ignored, and that every other market is in equilibrium, so that there are no changes from other markets that are impinging on the equilibrium in the market under consideration.

Neither of these assumptions is strictly true in theory, so all partial equilibrium analysis involves a certain amount of hand-waving. Nor, even if we wanted to be careful and precise, could we actually dispense with the hand-waving; the hand-waving is built into the analysis, and can’t be avoided. I have often referred to these assumptions required for the partial-equilibrium analysis — the bread and butter microeconomic analysis of Econ 101 — to be valid as the macroeconomic foundations of microeconomics, by which I mean that the casual assumption that microeconomics somehow has a privileged and secure theoretical position compared to macroeconomics and that macroeconomic propositions are only valid insofar as they can be reduced to more basic microeconomic principles is entirely unjustified. That doesn’t mean that we shouldn’t care about reconciling macroeconomics with microeconomics; it just means that the validity of proposition in macroeconomics is not necessarily contingent on being derived from microeconomics. Reducing macroeconomics to microeconomics should be an analytical challenge, not a methodological imperative.

So the assumption, derived from Modigliani’s 1944 paper that “price stickiness” is what prevents an economic system from moving automatically to a new equilibrium after being subjected to some shock or disturbance, reflects either a misunderstanding or a semantic confusion. It is not price stickiness that prevents the system from moving toward equilibrium, it is the fact that individuals are engaging in transactions at disequilibrium prices. We simply do not know how to compare different sets of non-equilibrium prices to determine which set of non-equilibrium prices will move the economy further from or closer to equilibrium. Our experience and out intuition suggest that in some neighborhood of equilibrium, an economy can absorb moderate shocks without going into a cumulative contraction. But all we really know from theory is that any trading at any set of non-equilibrium prices can trigger an economic contraction, and once it starts to occur, a contraction may become cumulative.

It is also a mistake to assume that in a world of incomplete markets, the missing markets being markets for the delivery of goods and the provision of services in the future, any set of price adjustments, however large, could by themselves ensure that equilibrium is restored. With an incomplete set of markets, economic agents base their decisions not just on actual prices in the existing markets; they base their decisions on prices for future goods and services which can only be guessed at. And it is only when individual expectations of those future prices are mutually consistent that equilibrium obtains. With inconsistent expectations of future prices, the adjustments in current prices in the markets that exist for currently supplied goods and services that in some sense equate amounts demanded and supplied, lead to a (temporary) equilibrium that is not efficient, one that could be associated with high unemployment and unused capacity even though technically existing markets are clearing.

So that’s why I regard the term “sticky prices” and other similar terms as very unhelpful and misleading; they are a kind of mental crutch that economists are too ready to rely on as a substitute for thinking about what are the actual causes of economic breakdowns, crises, recessions, and depressions. Most of all, they represent an uncritical transfer of partial-equilibrium microeconomic thinking to a problem that requires a system-wide macroeconomic approach. That approach should not ignore microeconomic reasoning, but it has to transcend both partial-equilibrium supply-demand analysis and the mathematics of intertemporal optimization.

Roger and Me

Last week Roger Farmer wrote a post elaborating on a comment that he had left to my post on Price Stickiness and Macroeconomics. Roger’s comment is aimed at this passage from my post:

[A]lthough price stickiness is a sufficient condition for inefficient macroeconomic fluctuations, it is not a necessary condition. It is entirely possible that even with highly flexible prices, there would still be inefficient macroeconomic fluctuations. And the reason why price flexibility, by itself, is no guarantee against macroeconomic contractions is that macroeconomic contractions are caused by disequilibrium prices, and disequilibrium prices can prevail regardless of how flexible prices are.

Here’s Roger’s comment:

I have a somewhat different take. I like Lucas’ insistence on equilibrium at every point in time as long as we recognize two facts. 1. There is a continuum of equilibria, both dynamic and steady state and 2. Almost all of them are Pareto suboptimal.

I made the following reply to Roger’s comment:

Roger, I think equilibrium at every point in time is ok if we distinguish between temporary and full equilibrium, but I don’t see how there can be a continuum of full equilibria when agents are making all kinds of long-term commitments by investing in specific capital. Having said that, I certainly agree with you that expectational shifts are very important in determining which equilibrium the economy winds up at.

To which Roger responded:

I am comfortable with temporary equilibrium as the guiding principle, as long as the equilibrium in each period is well defined. By that, I mean that, taking expectations as given in each period, each market clears according to some well defined principle. In classical models, that principle is the equality of demand and supply in a Walrasian auction. I do not think that is the right equilibrium concept.

Roger didn’t explain – at least not here, he probably has elsewhere — exactly why he doesn’t think equality of demand and supply in a Walrasian auction is not the right equilibrium concept. But I would be interested in hearing from him why he thinks equality of supply and demand is not the right equilibrium concept. Perhaps he will clarify his thinking for me.

Hicks wanted to separate ‘fix price markets’ from ‘flex price markets’. I don’t think that is the right equilibrium concept either. I prefer to use competitive search equilibrium for the labor market. Search equilibrium leads to indeterminacy because there are not enough prices for the inputs to the search process. Classical search theory closes that gap with an arbitrary Nash bargaining weight. I prefer to close it by making expectations fundamental [a proposition I have advanced on this blog].

I agree that the Hicksian distinction between fix-price markets and flex-price markets doesn’t cut it. Nevertheless, it’s not clear to me that a Thompsonian temporary-equilibrium model in which expectations determine the reservation wage at which workers will accept employment (i.e, the labor-supply curve conditional on the expected wage) doesn’t work as well as a competitive search equilibrium in this context.

Once one treats expectations as fundamental, there is no longer a multiplicity of equilibria. People act in a well defined way and prices clear markets. Of course ‘market clearing’ in a search market may involve unemployment that is considerably higher than the unemployment rate that would be chosen by a social planner. And when there is steady state indeterminacy, as there is in my work, shocks to beliefs may lead the economy to one of a continuum of steady state equilibria.

There is an equilibrium for each set of expectations (with the understanding, I presume, that expectations are always uniform across agents). The problem that I see with this is that there doesn’t seem to be any interaction between outcomes and expectations. Expectations are always self-fulfilling, and changes in expectations are purely exogenous. But in a classic downturn, the process seems to be cumulative, the contraction seemingly feeding on itself, causing a spiral of falling prices, declining output, rising unemployment, and increasing pessimism.

That brings me to the second part of an equilibrium concept. Are expectations rational in the sense that subjective probability measures over future outcomes coincide with realized probability measures? That is not a property of the real world. It is a consistency property for a model.

Yes; I agree totally. Rational expectations is best understood as a property of a model, the property being that if agents expect an equilibrium price vector the solution of the model is the same equilibrium price vector. It is not a substantive theory of expectation formation, the model doesn’t posit that agents correctly foresee the equilibrium price vector, that’s an extreme and unrealistic assumption about how the world actually works, IMHO. The distinction is crucial, but it seems to me that it is largely ignored in practice.

And yes: if we plop our agents down into a stationary environment, their beliefs should eventually coincide with reality.

This seems to me a plausible-sounding assumption for which there is no theoretical proof, and in view of Roger’s recent discussion of unit roots, dubious empirical support.

If the environment changes in an unpredictable way, it is the belief function, a primitive of the model, that guides the economy to a new steady state. And I can envision models where expectations on the transition path are systematically wrong.

I need to read Roger’s papers about this, but I am left wondering by what mechanism the belief function guides the economy to a steady state? It seems to me that the result requires some pretty strong assumptions.

The recent ‘nonlinearity debate’ on the blogs confuses the existence of multiple steady states in a dynamic model with the existence of multiple rational expectations equilibria. Nonlinearity is neither necessary nor sufficient for the existence of multiplicity. A linear model can have a unique indeterminate steady state associated with an infinite dimensional continuum of locally stable rational expectations equilibria. A linear model can also have a continuum of attracting points, each of which is an equilibrium. These are not just curiosities. Both of these properties characterize modern dynamic equilibrium models of the real economy.

I’m afraid that I don’t quite get the distinction that is being made here. Does “multiple steady states in a dynamic model” mean multiple equilibria of the full Arrow-Debreu general equilibrium model? And does “multiple rational-expectations equilibria” mean multiple equilibria conditional on the expectations of the agents? And I also am not sure what the import of this distinction is supposed to be.

My further question is, how does all of this relate to Leijonhfuvud’s idea of the corridor, which Roger has endorsed? My own understanding of what Axel means by the corridor is that the corridor has certain stability properties that keep the economy from careening out of control, i.e. becoming subject to a cumulative dynamic process that does not lead the economy back to the neighborhood of a stable equilibrium. But if there is a continuum of attracting points, each of which is an equilibrium, how could any of those points be understood to be outside the corridor?

Anyway, those are my questions. I am hoping that Roger can enlighten me.

Hicks on IS-LM and Temporary Equilibrium

Jan, commenting on my recent post about Krugman, Minsky and IS-LM, quoted the penultimate paragraph of J. R. Hicks’s 1980 paper on IS-LM in the Journal of Post-Keynesian Economics, a brand of economics not particularly sympathetic to Hicks’s invention. Hicks explained that in the mid-1930s he had been thinking along lines similar to Keynes’s even before the General Theory was published, and had the basic idea of IS-LM in his mind even before he had read the General Theory, while also acknowledging that his enthusiasm for the IS-LM construct had waned considerably over the years.

Hicks discussed both the similarities and the differences between his model and IS-LM. But as the discussion proceeds, it becomes clear that what he is thinking of as his model is what became his model of temporary equilibrium in Value and Capital. So it really is important to understand what Hicks felt were the similarities as well as the key differences between the temporary- equilibrium model, and the IS-LM model. Here is how Hicks put it:

I recognized immediately, as soon as I read The General Theory, that my model and Keynes’ had some things in common. Both of us fixed our attention on the behavior of an economy during a period—a period that had a past, which nothing that was done during the period could alter, and a future, which during the period was unknown. Expectations of the future would nevertheless affect what happened during the period. Neither of us made any assumption about “rational expectations” ; expectations, in our models, were strictly exogenous.3 (Keynes made much more fuss over that than I did, but there is the same implication in my model also.) Subject to these data— the given equipment carried over from the past, the production possibilities within the period, the preference schedules, and the given expectations— the actual performance of the economy within the period was supposed to be determined, or determinable. It would be determined as an equilibrium performance, with respect to these data.

There was all this in common between my model and Keynes’; it was enough to make me recognize, as soon as I saw The General Theory, that his model was a relation of mine and, as such, one which I could warmly welcome. There were, however, two differences, on which (as we shall see) much depends. The more obvious difference was that mine was a flexprice model, a perfect competition model, in which all prices were flexible, while in Keynes’ the level of money wages (at least) was exogenously determined. So Keynes’ was a model that was consistent with unemployment, while mine, in his terms, was a full employment model. I shall have much to say about this difference, but I may as well note, at the start, that I do not think it matters much. I did not think, even in 1936, that it mattered much. IS-LM was in fact a translation of Keynes’ nonflexprice model into my terms. It seemed to me already that that could be done; but how it is done requires explanation.

The other difference is more fundamental; it concerns the length of the period. Keynes’ (he said) was a “short-period,” a term with connotations derived from Marshall; we shall not go far wrong if we think of it as a year. Mine was an “ultra-short-period” ; I called it a week. Much more can happen in a year than in a week; Keynes has to allow for quite a lot of things to happen. I wanted to avoid so much happening, so that my (flexprice) markets could reflect propensities (and expectations) as they are at a moment. So it was that I made my markets open only on a Monday; what actually happened during the ensuing week was not to affect them. This was a very artificial device, not (I would think now) much to be recommended. But the point of it was to exclude the things which might happen, and must disturb the markets, during a period of finite length; and this, as we shall see, is a very real trouble in Keynes. (pp. 139-40)

Hicks then explained how the specific idea of the IS-LM model came to him as a result of working on a three-good Walrasian system in which the solution could be described in terms of equilibrium in two markets, the third market necessarily being in equilibrium if the other two were in equilibrium. That’s an interesting historical tidbit, but the point that I want to discuss is what I think is Hicks’s failure to fully understand the significance of his own model, whose importance, regrettably, he consistently underestimated in later work (e.g., in Capital and Growth and in this paper).

The point that I want to focus on is in the second paragraph quoted above where Hicks says “mine [i.e. temporary equilibrium] was a flexprice model, a perfect competition model, in which all prices were flexible, while in Keynes’ the level of money wages (at least) was exogenously determined. So Keynes’ was a model that was consistent with unemployment, while mine, in his terms, was a full employment model.” This, it seems to me, is all wrong, because Hicks, is taking a very naïve and misguided view of what perfect competition and flexible prices mean. Those terms are often mistakenly assumed to meant that if prices are simply allowed to adjust freely, all  markets will clear and all resources will be utilized.

I think that is a total misconception, and the significance of the temporary-equilibrium construct is in helping us understand why an economy can operate sub-optimally with idle resources even when there is perfect competition and markets “clear.” What prevents optimality and allows resources to remain idle despite freely adjustming prices and perfect competition is that the expectations held by agents are not consistent. If expectations are not consistent, the plans based on those expectations are not consistent. If plans are not consistent, then how can one expect resources to be used optimally or even at all? Thus, for Hicks to assert, casually without explicit qualification, that his temporary-equilibrium model was a full-employment model, indicates to me that Hicks was unaware of the deeper significance of his own model.

If we take a full equilibrium as our benchmark, and look at how one of the markets in that full equilibrium clears, we can imagine the equilibrium as the intersection of a supply curve and a demand curve, whose positions in the standard price/quantity space depend on the price expectations of suppliers and of demanders. Different, i.e, inconsistent, price expectations would imply shifts in both the demand and supply curves from those corresponding to full intertemporal equilibrium. Overall, the price expectations consistent with a full intertemporal equilibrium will in some sense maximize total output and employment, so when price expectations are inconsistent with full intertemporal equilibrium, the shifts of the demand and supply curves will be such that they will intersect at points corresponding to less output and less employment than would have been the case in full intertemporal equilibrium. In fact, it is possible to imagine that expectations on the supply side and the demand side are so inconsistent that the point of intersection between the demand and supply curves corresponds to an output (and hence employment) that is way less than it would have been in full intertemporal equilibrium. The problem is not that the price in the market doesn’t allow the market to clear. Rather, given the positions of the demand and supply curves, their point of intersection implies a low output, because inconsistent price expectations are such that potentially advantageous trading opportunities are not being recognized.

So for Hicks to assert that his flexprice temporary-equilibrium model was (in Keynes’s terms) a full-employment model without noting the possibility of a significant contraction of output (and employment) in a perfectly competitive flexprice temporary-equilibrium model when there are significant inconsistencies in expectations suggests strongly that Hicks somehow did not fully comprehend what his own creation was all about. His failure to comprehend his own model also explains why he felt the need to abandon the flexprice temporary-equilibrium model in his later work for a fixprice model.

There is, of course, a lot more to be said about all this, and Hicks’s comments concerning the choice of a length of the period are also of interest, but the clear (or so it seems to me) misunderstanding by Hicks of what is entailed by a flexprice temporary equilibrium is an important point to recognize in evaluating both Hicks’s work and his commentary on that work and its relation to Keynes.

Temporary Equilibrium One More Time

It’s always nice to be noticed, especially by Paul Krugman. So I am not upset, but in his response to my previous post, I don’t think that Krugman quite understood what I was trying to convey. I will try to be clearer this time. It will be easiest if I just quote from his post and insert my comments or explanations.

Glasner is right to say that the Hicksian IS-LM analysis comes most directly not out of Keynes but out of Hicks’s own Value and Capital, which introduced the concept of “temporary equilibrium”.

Actually, that’s not what I was trying to say. I wasn’t making any explicit connection between Hicks’s temporary-equilibrium concept from Value and Capital and the IS-LM model that he introduced two years earlier in his paper on Keynes and the Classics. Of course that doesn’t mean that the temporary equilibrium method isn’t connected to the IS-LM model; one would need to do a more in-depth study than I have done of Hicks’s intellectual development to determine how much IS-LM was influenced by Hicks’s interest in intertemporal equilibrium and in the method of temporary equilibrium as a way of analyzing intertemporal issues.

This involves using quasi-static methods to analyze a dynamic economy, not because you don’t realize that it’s dynamic, but simply as a tool. In particular, V&C discussed at some length a temporary equilibrium in a three-sector economy, with goods, bonds, and money; that’s essentially full-employment IS-LM, which becomes the 1937 version with some price stickiness. I wrote about that a long time ago.

Now I do think that it’s fair to say that the IS-LM model was very much in the spirit of Value and Capital, in which Hicks deployed an explicit general-equilibrium model to analyze an economy at a Keynesian level of aggregation: goods, bonds, and money. But the temporary-equilibrium aspect of Value and Capital went beyond the Keynesian analysis, because the temporary equilibrium analysis was explicitly intertemporal, all agents formulating plans based on explicit future price expectations, and the inconsistency between expected prices and actual prices was explicitly noted, while in the General Theory, and in IS-LM, price expectations were kept in the background, making an appearance only in the discussion of the marginal efficiency of capital.

So is IS-LM really Keynesian? I think yes — there is a lot of temporary equilibrium in The General Theory, even if there’s other stuff too. As I wrote in the last post, one key thing that distinguished TGT from earlier business cycle theorizing was precisely that it stopped trying to tell a dynamic story — no more periods, forced saving, boom and bust, instead a focus on how economies can stay depressed. Anyway, does it matter? The real question is whether the method of temporary equilibrium is useful.

That is precisely where I think Krugman’s grasp on the concept of temporary equilibrium is slipping. Temporary equilibrium is indeed about periods, and it is explicitly dynamic. In my previous post I referred to Hicks’s discussion in Capital and Growth, about 25 years after writing Value and Capital, in which he wrote

The Temporary Equilibrium model of Value and Capital, also, is “quasi-static” [like the Keynes theory] – in just the same sense. The reason why I was contented with such a model was because I had my eyes fixed on Keynes.

As I read this passage now — and it really bothered me when I read it as I was writing my previous post — I realize that what Hicks was saying was that his desire to conform to the Keynesian paradigm led him to compromise the integrity of the temporary equilibrium model, by forcing it to be “quasi-static” when it really was essentially dynamic. The challenge has been to convert a “quasi-static” IS-LM model into something closer to the temporary-equilibrium method that Hicks introduced, but did not fully execute in Value and Capital.

What are the alternatives? One — which took over much of macro — is to do intertemporal equilibrium all the way, with consumers making lifetime consumption plans, prices set with the future rationally expected, and so on. That’s DSGE — and I think Glasner and I agree that this hasn’t worked out too well. In fact, economists who never learned temporary-equiibrium-style modeling have had a strong tendency to reinvent pre-Keynesian fallacies (cough-Say’s Law-cough), because they don’t know how to think out of the forever-equilibrium straitjacket.

Yes, I agree! Rational expectations, full-equilibrium models have turned out to be a regression, not an advance. But the way I would make the point is that the temporary-equilibrium method provides a sort of a middle way to do intertemporal dynamics without presuming that consumption plans and investment plans are always optimal.

What about disequilibrium dynamics all the way? Basically, I have never seen anyone pull this off. Like the forever-equilibrium types, constant-disequilibrium theorists have a remarkable tendency to make elementary conceptual mistakes.

Again, I agree. We can’t work without some sort of equilibrium conditions, but temporary equilibrium provides a way to keep the discipline of equilibrium without assuming (nearly) full optimality.

Still, Glasner says that temporary equilibrium must involve disappointed expectations, and fails to take account of the dynamics that must result as expectations are revised.

Perhaps I was unclear, but I thought I was saying just the opposite. It’s the “quasi-static” IS-LM model, not temporary equilibrium, that fails to take account of the dynamics produced by revised expectations.

I guess I’d say two things. First, I’m not sure that this is always true. Hicks did indeed assume static expectations — the future will be like the present; but in Keynes’s vision of an economy stuck in sustained depression, such static expectations will be more or less right.

Again, I agree. There may be self-fulfilling expectations of a low-income, low-employment equilibrium. But I don’t think that that is the only explanation for such a situation, and certainly not for the downturn that can lead to such an equilibrium.

Second, those of us who use temporary equilibrium often do think in terms of dynamics as expectations adjust. In fact, you could say that the textbook story of how the short-run aggregate supply curve adjusts over time, eventually restoring full employment, is just that kind of thing. It’s not a great story, but it is the kind of dynamics Glasner wants — and it’s Econ 101 stuff.

Again, I agree. It’s not a great story, but, like it or not, the story is not a Keynesian story.

So where does this leave us? I’m not sure, but my impression is that Krugman, in his admiration for the IS-LM model, is trying too hard to identify IS-LM with the temporary-equilibrium approach, which I think represented a major conceptual advance over both the Keynesian model and the IS-LM representation of the Keynesian model. Temporary equilibrium and IS-LM are not necessarily inconsistent, but I mainly wanted to point out that the two aren’t the same, and shouldn’t be conflated.

Krugman on Minsky, IS-LM and Temporary Equilibrium

Catching up on my blog reading, I found this one from Paul Krugman from almost two weeks ago defending the IS-LM model against Hyman Minsky’s criticism (channeled by his student Lars Syll) that IS-LM misrepresented the message of Keynes’s General Theory. That is an old debate, and it’s a debate that will never be resolved because IS-LM is a nice way of incorporating monetary effects into the pure income-expenditure model that was the basis of Keynes’s multiplier analysis and his policy prescriptions. On the other hand, the model leaves out much of what most interesting and insightful in the General Theory — precisely the stuff that could not easily be distilled into a simple analytic model.

Here’s Krugman:

Lars Syll approvingly quotes Hyman Minsky denouncing IS-LM analysis as an “obfuscation” of Keynes; Brad DeLong disagrees. As you might guess, so do I.

There are really two questions here. The less important is whether something like IS-LM — a static, equilibrium analysis of output and employment that takes expectations and financial conditions as given — does violence to the spirit of Keynes. Why isn’t this all that important? Because Keynes was a smart guy, not a prophet. The General Theory is interesting and inspiring, but not holy writ.

It’s also a protean work that contains a lot of different ideas, not necessarily consistent with each other. Still, when I read Minsky putting into Keynes’s mouth the claim that

Only a theory that was explicitly cyclical and overtly financial was capable of being useful

I have to wonder whether he really read the book! As I read the General Theory — and I’ve read it carefully — one of Keynes’s central insights was precisely that you wanted to step back from thinking about the business cycle. Previous thinkers had focused all their energy on trying to explain booms and busts; Keynes argued that the real thing that needed explanation was the way the economy seemed to spend prolonged periods in a state of underemployment:

[I]t is an outstanding characteristic of the economic system in which we live that, whilst it is subject to severe fluctuations in respect of output and employment, it is not violently unstable. Indeed it seems capable of remaining in a chronic condition of subnormal activity for a considerable period without any marked tendency either towards recovery or towards complete collapse.

So Keynes started with a, yes, equilibrium model of a depressed economy. He then went on to offer thoughts about how changes in animal spirits could alter this equilibrium; but he waited until Chapter 22 (!) to sketch out a story about the business cycle, and made it clear that this was not the centerpiece of his theory. Yes, I know that he later wrote an article claiming that it was all about the instability of expectations, but the book is what changed economics, and that’s not what it says.

This all seems pretty sensible to me. Nevertheless, there is so much in the General Theory — both good and bad – that isn’t reflected in IS-LM, that to reduce the General Theory to IS-LM is a kind of misrepresentation. And to be fair, Hicks himself acknowledged that IS-LM was merely a way of representing one critical difference in the assumptions underlying the Keynesian and the “Classical” analyses of macroeconomic equilibrium.

But I would take issue with the following assertion by Krugman.

The point is that Keynes very much made use of the method of temporary equilibrium — interpreting the state of the economy in the short run as if it were a static equilibrium with a lot of stuff taken provisionally as given — as a way to clarify thought. And the larger point is that he was right to do this.

When people like me use something like IS-LM, we’re not imagining that the IS curve is fixed in position for ever after. It’s a ceteris paribus thing, just like supply and demand. Assuming short-run equilibrium in some things — in this case interest rates and output — doesn’t mean that you’ve forgotten that things change, it’s just a way to clarify your thought. And the truth is that people who try to think in terms of everything being dynamic all at once almost always end up either confused or engaging in a lot of implicit theorizing they don’t even realize they’re doing.

When I think of a temporary equilibrium, the most important – indeed the defining — characteristic of that temporary equilibrium is that expectations of at least some agents have been disappointed. The disappointment of expectations is likely to, but does not strictly require, a revision of disappointed expectations and of the plans conditioned on those expectations. The revision of expectations and plans as a result of expectations being disappointed is what gives rise to a dynamic adjustment process. But that is precisely what is excluded from – or at least not explicitly taken into account by – the IS-LM model. There is nothing in the IS-LM model that provides any direct insight into the process by which expectations are revised as a result of being disappointed. That Keynes could so easily think in terms of a depressed economy being in equilibrium suggests to me that he was missing what I regard as the key insight of the temporary-equilibrium method.

Of course, there are those who argue, perhaps most notably Roger Farmer, that economies have multiple equilibria, each with different levels of output and employment corresponding to different expectational parameters. That seems to me a more Keynesian approach, an approach recognizing that expectations can be self-fulfilling, than the temporary-equilibrium approach in which the focus is on mistaken and conflicting expectations, not their self-fulfillment.

Now to be fair, I have to admit that Hicks, himself, who introduced the temporary-equilibrium approach in Value and Capital (1939) later (1965) suggested in Capital and Growth (p. 65) that both the Keynes in the General Theory and the temporary-equilibrium approach of Value and Capital were “quasi-static.” The analysis of the General Theory “is not the analysis of a process; no means has been provided by which we can pass from one Keynesian period to the next. . . . The Temporary Equilibrium model of Value and Capital, also, is quasi-static in just the same sense. The reason why I was contented with such a model was because I had my eyes fixed on Keynes.

Despite Hicks’s identification of the temporary-equilibrium method with Keynes’s method in the General Theory, I think that Hicks was overly modest in assessing his own contribution in Value and Capital, failing to appreciate the full significance of the method he had introduced. Which, I suppose, just goes to show that you can’t assume that the person who invents a concept or an idea is necessarily the one who has the best, or most comprehensive, understanding of what the concept means of what its significance is.

Paul Krugman and Roger Farmer on Sticky Wages

I was pleasantly surprised last Friday to see that Paul Krugman took favorable notice of my post about sticky wages, but also registering some disagreement.

[Glasner] is partially right in suggesting that there has been a bit of a role reversal regarding the role of sticky wages in recessions: Keynes asserted that wage flexibility would not help, but Keynes’s self-proclaimed heirs ended up putting downward nominal wage rigidity at the core of their analysis. By the way, this didn’t start with the New Keynesians; way back in the 1940s Franco Modigliani had already taught us to think that everything depended on M/w, the ratio of the money supply to the wage rate.

That said, wage stickiness plays a bigger role in The General Theory — and in modern discussions that are consistent with what Keynes said — than Glasner indicates.

To document his assertion about Keynes, Krugman quotes a passage from the General Theory in which Keynes seems to suggest that in the nineteenth century inflexible wages were partially compensated for by price level movements. One might quibble with Krugman’s interpretation, but the payoff doesn’t seem worth the effort.

But I will quibble with the next paragraph in Krugman’s post.

But there’s another point: even if you don’t think wage flexibility would help in our current situation (and like Keynes, I think it wouldn’t), Keynesians still need a sticky-wage story to make the facts consistent with involuntary unemployment. For if wages were flexible, an excess supply of labor should be reflected in ever-falling wages. If you want to say that we have lots of willing workers unable to find jobs — as opposed to moochers not really seeking work because they’re cradled in Paul Ryan’s hammock — you have to have a story about why wages aren’t falling.

Not that I really disagree with Krugman that the behavior of wages since the 2008 downturn is consistent with some stickiness in wages. Nevertheless, it is still not necessarily the case that, if wages were flexible, an excess supply of labor would lead to ever-falling wages. In a search model of unemployment, if workers are expecting wages to rise every year at a 3% rate, and instead wages rise at only a 1% rate, the model predicts that unemployment will rise, and will continue to rise (or at least not return to the natural rate) as long as observed wages did not increase as fast as workers were expecting wages to rise. Presumably over time, wage expectations would adjust to a new lower rate of increase, but there is no guarantee that the transition would be speedy.

Krugman concludes:

So sticky wages are an important part of both old and new Keynesian analysis, not because wage cuts would help us, but simply to make sense of what we see.

My own view is actually a bit more guarded. I think that “sticky wages” is simply a name that we apply to a problematic phenomenon for ehich we still haven’t found a really satisfactory explanation for. Search models, for all their theoretical elegance, simply can’t explain the observed process by which unemployment rises during recessions, i.e., by layoffs and a lack of job openings rather than an increase in quits and refused offers, as search models imply. The suggestion in my earlier post was intended to offer a possible basis of understanding what the phrase “sticky wages” is actually describing.

Roger Farmer, a long-time and renowned UCLA economist, also commented on my post on his new blog. Welcome to the blogosphere, Roger.

Roger has a different take on the sticky-wage phenomenon. Roger argues, as did some of the commenters to my post, that wages are not sticky. To document this assertion, Roger presents a diagram showing that the decline of nominal wages closely tracked that of prices for the first six years of the Great Depression. From this evidence Roger concludes that nominal wage rigidity is not the cause of rising unemployment during the Great Depression, and presumably, not the cause of rising unemployment in the Little Depression.

farmer_sticky_wagesInstead, Roger argues, the rise in unemployment was caused by an outbreak of self-fulfilling pessimism. Roger believes that there are many alternative equilibria and which equilibrium (actually equilibrium time path) we reach depends on what our expectations are. Roger also believes that our expectations are rational, so that we get what we expect, as he succinctly phrases it “beliefs are fundamental.” I have a lot of sympathy for this way of looking at the economy. In fact one of the early posts on this blog was entitled “Expectations are Fundamental.” But as I have explained in other posts, I am not so sure that expectations are rational in any useful sense, because I think that individual expectations diverge. I don’t think that there is a single way of looking at reality. If there are many potential equilibria, why should everyone expect the same equilibrium. I can be an optimist, and you can be a pessimist. If we agreed, we would be right, but if we disagree, we will both be wrong. What economic mechanism is there to reconcile our expectations? In a world in which expectations diverge — a world of temporary equilibrium — there can be cumulative output reductions that get propagated across the economy as each sector fails to produce its maximum potential output, thereby reducing the demand for the output of other sectors to which it is linked. That’s what happens when there is trading at prices that don’t correspond to the full optimum equilibrium solution.

So I agree with Roger in part, but I think that the coordination problem is (at least potentially) more serious than he imagines.

Big Ideas in Macroeconomics: A Review

Steve Williamson recently plugged a new book by Kartik Athreya (Big Ideas in Macroeconomics), an economist at the Federal Reserve Bank of Richmond, which tries to explain in relatively non-technical terms what modern macroeconomics is all about. I will acknowledge that my graduate training in macroeconomics predated the rise of modern macro, and I am not fluent in the language of modern macro, though I am trying to fill in the gaps. And this book is a good place to start. I found Athreya’s book a good overview of the field, explaining the fundamental ideas and how they fit together.

Big Ideas in Macroeconomics is a moderately big book, 415 pages, covering a very wide range of topics. It is noteworthy, I think, that despite its size, there is so little overlap between the topics covered in this book, and those covered in more traditional, perhaps old-fashioned, books on macroeconomics. The index contains not a single entry on the price level, inflation, deflation, money, interest, total output, employment or unemployment. Which is not to say that none of those concepts are ever mentioned or discussed, just that they are not treated, as they are in traditional macroeconomics books, as the principal objects of macroeconomic inquiry. The conduct of monetary or fiscal policy to achieve some explicit macroeconomic objective is never discussed. In contrast, there are repeated references to Walrasian equilibrium, the Arrow-Debreu-McKenzie model, the Radner model, Nash-equilibria, Pareto optimality, the first and second Welfare theorems. It’s a new world.

The first two chapters present a fairly detailed description of the idea of Walrasian general equilibrium and its modern incarnation in the canonical Arrow-Debreu-McKenzie (ADM) model.The ADM model describes an economy of utility-maximizing households and profit-maximizing firms engaged in the production and consumption of commodities through time and space. There are markets for commodities dated by time period, specified by location and classified by foreseeable contingent states of the world, so that the same physical commodity corresponds to many separate commodities, each corresponding to different time periods and locations and to contingent states of the world. Prices for such physically identical commodities are not necessarily uniform across times, locations or contingent states.The demand for road salt to de-ice roads depends on whether conditions, which depend on time and location and on states of the world. For each different possible weather contingency, there would be a distinct market for road salt for each location and time period.

The ADM model is solved once for all time periods and all states of the world. Under appropriate conditions, there is one (and possibly more than one) intertemporal equilibrium, all trades being executed in advance, with all deliveries subsequently being carried out, as time an contingencies unfold, in accordance with the terms of the original contracts.

Given the existence of an equilibrium, i.e., a set of prices subject to which all agents are individually optimizing, and all markets are clearing, there are two classical welfare theorems stating that any such equilibrium involves a Pareto-optimal allocation and any Pareto-optimal allocation could be supported by an equilibrium set of prices corresponding to a suitably chosen set of initial endowments. For these optimality results to obtain, it is necessary that markets be complete in the sense that there is a market for each commodity in each time period and contingent state of the world. Without a complete set of markets in this sense, the Pareto-optimality of the Walrasian equilibrium cannot be proved.

Readers may wonder about the process by which an equilibrium price vector would actually be found through some trading process. Athreya invokes the fiction of a Walrasian clearinghouse in which all agents (truthfully) register their notional demands and supplies at alternative price vectors. Based on these responses the clearinghouse is able to determine, by a process of trial and error, the equilibrium price vector. Since the Walrasian clearinghouse presumes that no trading occurs except at an equilibrium price vector, there can be no assurance that an equilibrium price vector would ever be arrived at under an actual trading process in which trading occurs at disequilibrium prices. Moreover, as Clower and Leijonhufvud showed over 40 years ago (“Say’s Principle: What it Means and What it Doesn’t Mean”), trading at disequilibrium prices may cause cumulative contractions of aggregate demand because the total volume of trade at a disequilibrium price will always be less than the volume of trade at an equilibrium price, the volume of trade being constrained by the lesser of quantity supplied and quantity demanded.

In the view of modern macroeconomics, then, Walrasian general equilibrium, as characterized by the ADM model, is the basic and overarching paradigm of macroeconomic analysis. To be sure, modern macroeconomics tries to go beyond the highly restrictive assumptions of the ADM model, but it is not clear whether the concessions made by modern macroeconomics to the real world go very far in enhancing the realism of the basic model.

Chapter 3, contains some interesting reflections on the importance of efficiency (Pareto-optimality) as a policy objective and on the trade-offs between efficiency and equity and between ex-ante and ex-post efficiency. But these topics are on the periphery of macroeconomics, so I will offer no comment here.

In chapter 4, Athreya turns to some common criticisms of modern macroeconomics: that it is too highly aggregated, too wedded to the rationality assumption, too focused on equilibrium steady states, and too highly mathematical. Athreya correctly points out that older macroeconomic models were also highly aggregated, so that if aggregation is a problem it is not unique to modern macroeconomics. That’s a fair point, but skirts some thorny issues. As Athreya acknowledges in chapter 5, an important issue separating certain older macroeconomic traditions (both Keynesian and Austrian among others) is the idea that macroeconomic dysfunction is a manifestation of coordination failure. It is a property – a remarkable property – of Walrasian general equilibrium that it achieves perfect (i.e., Pareto-optimal) coordination of disparate, self-interested, competitive individual agents, fully reconciling their plans in a way that might have been achieved by an omniscient and benevolent central planner. Walrasian general equilibrium fully solves the coordination problem. Insofar as important results of modern macroeconomics depend on the assumption that a real-life economy can be realistically characterized as a Walrasian equilibrium, modern macroeconomics is assuming that coordination failures are irrelevant to macroeconomics. It is only after coordination failures have been excluded from the purview of macroeconomics that it became legitimate (for the sake of mathematical tractability) to deploy representative-agent models in macroeconomics, a coordination failure being tantamount, in the context of a representative agent model, to a form of irrationality on the part of the representative agent. Athreya characterizes choices about the level of aggregation as a trade-off between realism and tractability, but it seems to me that, rather than making a trade-off between realism and tractability, modern macroeconomics has simply made an a priori decision that coordination problems are not a relevant macroeconomic concern.

A similar argument applies to Athreya’s defense of rational expectations and the use of equilibrium in modern macroeconomic models. I would not deny that there are good reasons to adopt rational expectations and full equilibrium in some modeling situations, depending on the problem that theorist is trying to address. The question is whether it can be appropriate to deviate from the assumption of a full rational-expectations equilibrium for the purposes of modeling fluctuations over the course of a business cycle, especially a deep cyclical downturn. In particular, the idea of a Hicksian temporary equilibrium in which agents hold divergent expectations about future prices, but markets clear period by period given those divergent expectations, seems to offer (as in, e.g., Thompson’s “Reformulation of Macroeconomic Theory“) more realism and richer empirical content than modern macromodels of rational expectations.

Athreya offers the following explanation and defense of rational expectations:

[Rational expectations] purports to explain the expectations people actually have about the relevant items in their own futures. It does so by asking that their expectations lead to economy-wide outcomes that do not contradict their views. By imposing the requirement that expectations not be systematically contradicted by outcomes, economists keep an unobservable object from becoming a source of “free parameters” through which we can cheaply claim to have “explained” some phenomenon. In other words, in rational-expectations models, expectations are part of what is solved for, and so they are not left to the discretion of the modeler to impose willy-nilly. In so doing, the assumption of rational expectations protects the public from economists.

This defense of rational expectations plainly belies betrays the methodological arrogance of modern macroeconomics. I am all in favor of solving a model for equilibrium expectations, but solving for equilibrium expectations is certainly not the same as insisting that the only interesting or relevant result of a model is the one generated by the assumption of full equilibrium under rational expectations. (Again see Thompson’s “Reformulation of Macroeconomic Theory” as well as the classic paper by Foley and Sidrauski, and this post by Rajiv Sethi on his blog.) It may be relevant and useful to look at a model and examine its properties in a state in which agents hold inconsistent expectations about future prices; the temporary equilibrium existing at a point in time does not correspond to a steady state. Why is such an equilibrium uninteresting and uninformative about what happens in a business cycle? But evidently modern macroeconomists such as Athreya consider it their duty to ban such models from polite discourse — certainly from the leading economics journals — lest the public be tainted by economists who might otherwise dare to abuse their models by making illicit assumptions about expectations formation and equilibrium concepts.

Chapter 5 is the most important chapter of the book. It is in this chapter that Athreya examines in more detail the kinds of adjustments that modern macroeconomists make in the Walrasian/ADM paradigm to accommodate the incompleteness of markets and the imperfections of expectation formation that limit the empirical relevance of the full ADM model as a macroeconomic paradigm. To do so, Athreya starts by explaining how the Radner model in which a less than the full complement of Arrow-Debreu contingent-laims markets is available. In the Radner model, unlike the ADM model, trading takes place through time for those markets that actually exist, so that the full Walrasian equilibrium exists only if agents are able to form correct expectations about future prices. And even if the full Walrasian equilibrium exists, in the absence of a complete set of Arrow-Debreu markets, the classical welfare theorems may not obtain.

To Athreya, these limitations on the Radner version of the Walrasian model seem manageable. After all, if no one really knows how to improve on the equilibrium of the Radner model, the potential existence of Pareto improvements to the Radner equilibrium is not necessarily that big a deal. Athreya expands on the discussion of the Radner model by introducing the neoclassical growth model in both its deterministic and stochastic versions, all the elements of the dynamic stochastic general equilibrium (DSGE) model that characterizes modern macroeconomics now being in place. Athreya closes out the chapter with additional discussions of the role of further modifications to the basic Walrasian paradigm, particularly search models and overlapping-generations models.

I found the discussion in chapter 5 highly informative and useful, but it doesn’t seem to me that Athreya faces up to the limitations of the Radner model or to the implied disconnect between the Walraisan paradigm and macroeconomic analysis. A full Walrasian equilibrium exists in the Radner model only if all agents correctly anticipate future prices. If they don’t correctly anticipate future prices, then we are in the world of Hicksian temporary equilibrium. But in that world, the kind of coordination failures that Athreya so casually dismisses seem all too likely to occur. In a world of temporary equilibrium, there is no guarantee that intertemporal budget constraints will be effective, because those budget constraint reflect expected, not actual, future prices, and, in temporary equilibrium, expected prices are not the same for all transactors. Budget constraints are not binding in a world in which trading takes place through time based on possibly incorrect expectations of future prices. Not only does this mean that all the standard equilibrium and optimality conditions of Walrasian theory are violated, but that defaults on IOUs and, thus, financial-market breakdowns, are entirely possible.

In a key passage in chapter 5, Athreya dismisses coordination-failure explanations, invidiously characterized as Keynesian, for inefficient declines in output and employment. While acknowledging that such fluctuations could, in theory, be caused by “self-fulfilling pessimism or fear,” Athreya invokes the benchmark Radner trading arrangement of the ADM model. “In the Radner economy, Athreya writes, “households and firms have correct expectations for the spot market prices one period hence.” The justification for that expectational assumption, which seems indistinguishable from the assumption of a full, rational-expectations equilibrium, is left unstated. Athreya continues:

Granting that they indeed have such expectations, we can now ask about the extent to which, in a modern economy, we can have outcomes that are extremely sensitive to them. In particular, is it the case that under fairly plausible conditions, “optimism” and “pessimism” can be self-fulfilling in ways that make everyone (or nearly everyone) better off in the former than the latter?

Athreya argues that this is possible only if the aggregate production function of the economy is characterized by increasing returns to scale, so that productivity increases as output rises.

[W]hat I have in mind is that the structure of the economy must be such that when, for example, all households suddenly defer consumption spending (and save instead), interest rates do not adjust rapidly to forestall such a fall in spending by encouraging firms to invest.

Notice that Athreya makes no distinction between a reduction in consumption in which people shift into long-term real or financial assets and one in which people shift into holding cash. The two cases are hardly identical, but Athreya has nothing to say about the demand for money and its role in macroeconomics.

If they did, under what I will later describe as a “standard” production side for the economy, wages would, barring any countervailing forces, promptly rise (as the capital stock rises and makes workers more productive). In turn, output would not fall in response to pessimism.

What Athreya is saying is that if we assume that there is a reduction in the time preference of households, causing them to defer present consumption in order to increase their future consumption, the shift in time preference should be reflected in a rise in asset prices, causing an increase in the production of durable assets, and leading to an increase in wages insofar as the increase in the stock of fixed capital implies an increase in the marginal product of labor. Thus, if all the consequences of increased thrift are foreseen at the moment that current demand for output falls, there would be a smooth transition from the previous steady state corresponding to a high rate of time preference to the new steady state corresponding to a low rate of time preference.

Fine. If you assume that the economy always remains in full equilibrium, even in the transition from one steady state to another, because everyone has rational expectations, you will avoid a lot of unpleasantness. But what if entrepreneurial expectations do not change instantaneously, and the reduction in current demand for output corresponding to reduced spending on consumption causes entrepreneurs to reduce, not increase, their demand for capital equipment? If, after the shift in time preference, total spending actually falls, there may be a chain of disappointments in expectations, and a series of defaults on IOUs, culminating in a financial crisis. Pessimism may indeed be self-fulfilling. But Athreya has a just-so story to tell, and he seems satisfied that there is no other story to be told. Others may not be so easily satisfied, especially when his just-so story depends on a) the rational expectations assumption that many smart people have a hard time accepting as even remotely plausible, and b) the assumption that no trading takes place at disequilibrium prices. Athreya continues:

Thus, at least within the context of models in which households and firms are not routinely incorrect about the future, multiple self-fulfilling outcomes require particular features of the production side of the economy to prevail.

Actually what Athreya should have said is: “within the context of models in which households and firms always predict future prices correctly.”

In chapter 6, Athreya discusses how modern macroeconomics can and has contributed to the understanding of the financial crisis of 2007-08 and the subsequent downturn and anemic recovery. There is a lot of very useful information and discussion of various issues, especially in connection with banking and financial markets. But further comment at this point would be largely repetitive.

Anyway, despite my obvious and strong disagreements with much of what I read, I learned a lot from Athreya’s well-written and stimulating book, and I actually enjoyed reading it.

What Kind of Equilibrium Is This?

In my previous post, I suggested that Stephen Williamson’s views about the incapacity of monetary policy to reduce unemployment, and his fears that monetary expansion would simply lead to higher inflation and a repeat of the bad old days the 1970s when inflation and unemployment spun out of control, follow from a theoretical presumption that the US economy is now operating (as it almost always does) in the neighborhood of equilibrium. This does not seem right to me, but it is the sort of deep theoretical assumption (e.g., like the rationality of economic agents) that is not subject to direct empirical testing. It is part of what the philosopher Imre Lakatos called the hard core of a (in this case Williamson’s) scientific research program. Whatever happens, Williamson will process the observed facts in terms of a theoretical paradigm in which prices adjust and markets clear. No other way of viewing reality makes sense, because Williamson cannot make any sense of it in terms of the theoretical paradigm or world view to which he is committed. I actually have some sympathy with that way of looking at the world, but not because I think it’s really true; it’s just the best paradigm we have at the moment. But I don’t want to follow that line of thought too far now, but who knows, maybe another time.

A good illustration of how Williamson understands his paradigm was provided by blogger J. P. Koning in his comment on my previous post copying the following quotation from a post written by Williamson a couple of years on his blog.

In other cases, as in the link you mention, there are people concerned about disequilibrium phenomena. These approaches are or were popular in Europe – I looked up Benassy and he is still hard at work. However, most of the mainstream – and here I’m including New Keynesians – sticks to equilibrium economics. New Keynesian models may have some stuck prices and wages, but those models don’t have to depart much from standard competitive equilibrium (or, if you like, competitive equilibrium with monopolistic competition). In those models, you have to determine what a firm with a stuck price produces, and that is where the big leap is. However, in terms of determining everything mathematically, it’s not a big deal. Equilibrium economics is hard enough as it is, without having to deal with the lack of discipline associated with “disequilibrium.” In equilibrium economics, particularly monetary equilibrium economics, we have all the equilibria (and more) we can handle, thanks.

I actually agree that departing from the assumption of equilibrium can involve a lack of discipline. Market clearing is a very powerful analytical tool, and to give it up without replacing it with an equally powerful analytical tool leaves us theoretically impoverished. But Williamson seems to suggest (or at least leaves ambiguous) that there is only one kind of equilibrium that can be handled theoretically, namely a fully optimal general equilibrium with perfect foresight (i.e., rational expectations) or at least with a learning process leading toward rational expectations. But there are other equilibrium concepts that preserve market clearing, but without imposing, what seems to me, the unreasonable condition of rational expectations and (near) optimality.

In particular, there is the Hicksian concept of a temporary equilibrium (inspired by Hayek’s discussion of intertemporal equilibrium) which allows for inconsistent expectations by economic agents, but assumes market clearing based on supply and demand schedules reflecting those inconsistent expectations. Nearly 40 years ago, Earl Thompson was able to deploy that equilibrium concept to derive a sub-optimal temporary equilibrium with Keynesian unemployment and a role for countercyclical monetary policy in minimizing inefficient unemployment. I have summarized and discussed Thompson’s model previously in some previous posts (here, here, here, and here), and I hope to do a few more in the future. The model is hardly the last word, but it might at least serve as a starting point for thinking seriously about the possibility that not every state of the economy is an optimal equilibrium state, but without abandoning market clearing as an analytical tool.

About Me

David Glasner
Washington, DC

I am an economist in the Washington DC area. My research and writing has been mostly on monetary economics and policy and the history of economics. In my book Free Banking and Monetary Reform, I argued for a non-Monetarist non-Keynesian approach to monetary policy, based on a theory of a competitive supply of money. Over the years, I have become increasingly impressed by the similarities between my approach and that of R. G. Hawtrey and hope to bring Hawtrey's unduly neglected contributions to the attention of a wider audience.

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