Archive for the 'Phillips Curve' Category

Making Sense of the Phillips Curve

In a comment on my previous post about supposedly vertical long run Phillips Curve, Richard Lipsey mentioned a paper he presented a couple of years ago at the History of Economics Society Meeting: “The Phillips Curve and the Tyranny of an Assumed Unique Macro Equilibrium.” In a subsequent comment, Richard also posted the abstract to his paper. The paper provides a succinct yet fascinating overview of the evolution macroeconomists’ interpretations of the Phillips curve since Phillips published his paper almost 60 years ago.

The two key points that I take away from Richard’s discussion are the following. 1) A key microeconomic assumption underlying the Keynesian model is that over a broad range of outputs, most firms are operating under conditions of constant short-run marginal cost, because in the short run firms keep the capital labor ratio fixed, varying their usage of capital along with the amount of labor utilized. With a fixed capital-labor ration, marginal cost is flat. In the usual textbook version, the short-run marginal cost is rising because of a declining capital-labor ratio, requiring an increasing number of workers to wring out successive equal increments of output from a fixed amount of capital. Given flat marginal cost, firms respond to changes in demand by varying output but not price until they hit a capacity bottleneck.

The second point, a straightforward implication of the first, is that there are multiple equilibria for such an economy, each equilibrium corresponding to a different level of total demand, with a price level more or less determined by costs, at any rate until total output approaches the limits of its capacity.

Thus, early on, the Phillips Curve was thought to be relatively flat, with little effect on inflation unless unemployment was forced down below some very low level. The key question was how far unemployment could be pushed down before significant inflationary pressure would begin to emerge. Doctrinaire Keynesians advocated driving unemployment down as low as possible, while skeptics argued that significant inflationary pressure would begin to emerge even at higher rates of unemployment, so that a prudent policy would be to operate at a level of unemployment sufficiently high to keep inflationary pressures in check.

Lipsey allows that, in the 1960s, the view that the Phillips Curve presented a menu of alternative combinations of unemployment and inflation from which policymakers could choose did take hold, acknowledging that he himself expressed such a view in a 1965 paper (“Structural and Deficient Demand Unemployment Reconsidered” in Employment Policy and the Labor Market edited by Arthur Ross), “inflationary points on the Phillips Curve represent[ing] disequilibrium points that had to be maintained by monetary policy that perpetuated the disequilibrium by suitable increases in the rate of monetary expansion.” It was this version of the Phillips Curve that was effectively attacked by Friedman and Phelps, who replaced it with a version in which the equilibrium rate of unemployment is uniquely determined by real factors, the natural rate of unemployment, any deviation from the natural rate resulting in a series of adjustments in inflation and expected inflation that would restore the natural rate of unemployment.

Sometime in the 1960s the Phillips curve came to be thought of as providing a stable trade-off between inflation and unemployment. When Lipsey did adopt this trade-off version, as for example Lipsey (1965), inflationary points on the Phillips curve represented disequilibrium points that had to be maintained by monetary policy that perpetuated the disequilibrium by suitable increases in the rate of monetary expansion. In the new Classical interpretation that began with Edmund Phelps (1967), Milton Friedman (1968) and Lucas and Rapping (1969), each point was an equilibrium point because demands and supplies of agents were shifted from their full-information locations when they misinterpreted the price signals. There was, however, only one full-information equilibrium of income, Y*, and unemployment, U*.

The Friedman-Phelps argument was made as inflation rose significantly in the late 1960s, and the mild 1969-70 recession reduce inflation by only a smidgen, setting the stage for Nixon’s imposition of his disastrous wage and price controls in 1971 combined with a loosening of monetary policy by a compliant Arthur Burns as part of Nixon’s 1972 reelection strategy. When the hangover to the 1972 monetary binge was combined with a quadrupling of oil prices by OPEC in late 1973, the result was a simultaneous increase in inflation and unemployment – stagflation — a combination widely perceived as a decisive refutation of Keynesian theory. To cope with that theoretical conundrum, the Keynesian model was expanded to incorporate the determination of the price level by deriving an aggregate supply and aggregate demand curve in price-level/output space.

Lipsey acknowledges a crucial misstep in constructing the Aggregate Demand/Aggregate Supply framework: assuming a unique macroeconomic equilibrium, an assumption that implied the existence of a unique natural rate of unemployment. Keynesians won the battle, providing a perfectly respectable theoretical explanation for stagflation, but, in doing so, they lost the war to Friedman, paving the way for the malign ascendancy of New Classical economics, with which New Keynesian economics became an effective collaborator. Whether the collaboration was willing or unwilling is unclear and unimportant; by assuming a unique equilibrium, New Keynesians gave up the game.

I was so intent in showing that this AD-AS construction provided a simple Keynesian explanation of stagflation, contrary to the accusation of the New Classical economists that stagflation provided a conclusive refutation of Keynesian economics that I paid too little attention to the enormous importance of the new assumption introduced into Keynesian models. The addition of an expectations-augmented Philips curve, negatively sloped in the short run but vertical in the long run, produced a unique macro equilibrium that would be reached whatever macroeconomic policy was adopted.

Lipsey does not want to go back to the old Keynesian paradigm; he prefers a third approach that can be traced back to, among others, Joseph Schumpeter in which the economy is viewed “as constantly evolving under the impact of endogenously generated technological change.” Such technological change can be vaguely foreseen, but also gives rise to genuine surprises. The course of economic development is not predetermined, but path-dependent. History matters.

I suggest that the explanation of the current behaviour of inflation, output and unemployment in modern industrial economies is provided not by any EWD [equilibrium with deviations] theory but by evolutionary theories. These build on the obvious observation that technological change is continual in modern economies (decade by decade at least since 1760), but uneven (tending to come in spurts), and path dependent (because, among other reasons, knowledge is cumulative with one advance enabling another). These changes are generated endogenously by private-sector, profit-seeking agents competing in terms of new products, new processes and new forms of organisation, and by public sector activities in such places as universities and government research laboratories. They continually alter the structure of the economy, causing waves of serially correlated investment expenditure that are a major cause of cycles, as well as driving the long-term growth that continually transforms our economic, social and political structures. In their important book As Time Goes By, Freeman and Louça (2001) trace these processes as they have operated since the beginnings of the First Industrial Revolution.

A critical distinction in all such theories is between risk, which is easily handled in neoclassical economics, and uncertainty, which is largely ignored in it except to pay it lip service. In risky situations, agents with the same objective function and identical knowledge will chose the same alternative: the one that maximizes the expected value of their profits or utility. This gives rise to unique predictable behaviour of agents acting under specified conditions. In contrast in uncertain situations, two identically situated and motivated agents can, and observably do, choose different alternatives — as for example when different firms all looking for the same technological breakthrough chose different lines of R&D — and there is no way to tell in advance of knowing the results which is the better choice. Importantly, agents typically make R&D decisions under conditions of genuine uncertainty. No one knows if a direction of technological investigation will go up a blind alley or open onto a rich field of applications until funds are spend investigating the route. Sometimes trivial expenses produce results of great value while major expenses produce nothing of value. Since there is no way to decide in advance which of two alternative actions with respect to invention or innovation is the best one until the results are known, there is no unique line of behaviour that maximises agents’ expected profits. Thus agents are better understood as groping into an uncertain future in a purposeful, profit- or utility-seeking manner, rather than as maximizing their profits or utility.

This is certainly the right way to think about how economies evolve over time, but I would just add that even if one stays within the more restricted framework of Walrasian general equilibrium, there is simply no persuasive theoretical reason to assume that there is a unique equilibrium or that an economy will necessarily arrive at that equilibrium no matter how long we wait. I have discussed this point several times before most recently here. The assumption that there is a natural rate of unemployment “ground out,” as Milton Friedman put it so awkwardly, “by the Walrasian system of general equilibrium equations” simply lacks any theoretical foundation. Even in a static model in which knowledge and technology were not evolving, the natural rate of unemployment is a will o the wisp.

Because there is no unique static equilibrium in the evolutionary world in which history matters, no adjustment mechanism is required to maintain it. Instead, the constantly changing economy can exist over a wide range of income, employment and unemployment values, without behaving as it would if its inflation rate were determined by an expectations-augmented Phillips curve or any similar construct centred on unique general equilibrium values of Y and U. Thus there is no stable long-run vertical Phillips curve or aggregate supply curve.

Instead of the Phillips curve there is a band as shown in Figure 4 [See below]. Its midpoint is at the expected rate of inflation. If the central bank has a credible inflation target that it sticks to, the expected rate will be that target rate, shown as πe in the figure. The actual rate will vary around the expected rate depending on a number of influences such as changes in productivity, the price of oil and food, but not significantly on variations in U or Y. At either end of this band, there may be something closer to a conventional Phillips curve with prices and wages falling in the face of a major depression and rising in the face of a major boom financed by monetary expansion. Also, the whole band will be shifted by anything that changes the expected rate of inflation.


Lipsey concludes as follows:

So we seem to have gone full circle from early Keynesian view in which there was no unique level of income to which the economy was inevitably drawn, through a simple Phillips curve with its implied trade off, to an expectations-augmented Phillips curve (or any of its more modern equivalents) with its associated unique level of national income, and finally back to the early non-unique Keynesian view in which policy makers had an option as to the average pressure of aggregate demand at which the economy could be operated.

“Perhaps [then] Keynesians were too hasty in following the New Classical economists in accepting the view that follows from static [and all EWD] models that stable rates of wage and price inflation are poised on the razor’s edge of a unique NAIRU and its accompanying Y*. The alternative does not require a long term Phillips curve trade off, nor does it deny the possibility of accelerating inflations of the kind that have bedevilled many third world countries. It is merely states that industrialised economies with low expected inflation rates may be less precisely responsive than current theory assumes because they are subject to many lags and inertias, and are operating in an ever-changing and uncertain world of endogenous technological change, which has no unique long term static equilibrium. If so, the economy may not be similar to the smoothly functioning mechanical world of Newtonian mechanics but rather to the imperfectly evolving world of evolutionary biology. The Phillips relation then changes from being a precise curve to being a band within which various combinations of inflation and unemployment are possible but outside of which inflation tends to accelerate or decelerate. Perhaps then the great [pre-Phillips curve] debates of the 1940s and early 1950s that assumed that there was a range within which the economy could be run with varying pressures of demand, and varying amounts of unemployment and inflation[ary pressure], were not as silly as they were made to seem when both Keynesian and New Classical economists accepted the assumption of a perfectly inelastic, one-dimensional, long run Phillips curve located at a unique equilibrium Y* and NAIRU.” (Lipsey, “The Phillips Curve,” In Famous Figures and Diagrams in Economics, edited by Mark Blaug and Peter Lloyd, p. 389)

The Near Irrelevance of the Vertical Long-Run Phillips Curve

From a discussion about how much credit Milton Friedman deserves for changing the way that economists thought about inflation, I want to nudge the conversation in a slightly different direction, to restate a point that I made some time ago in one of my favorite posts (The Lucas Critique Revisited). But if Friedman taught us anything it is that incessant repetition of the same already obvious point can do wonders for your reputation. That’s one lesson from Milton that I am willing to take to heart, though my tolerance for hearing myself say the same darn thing over and over again is probably not as great as Friedman’s was, which to be sure is not the only way in which I fall short of him by comparison. (I am almost a foot taller than he was by the way). Speaking of being a foot taller than Friedman, I don’t usually post pictures on this blog, but here is one that I have always found rather touching. And if you don’t know who the other guy is in the picture, you have no right to call yourself an economist.

friedman_&_StiglerAt any rate, the expectations augmented, long-run Phillips Curve, as we all know, was shown by Friedman to be vertical. But what exactly does it mean for the expectations-augmented, long-run Phillips Curve to be vertical? Discussions about whether the evidence supports the proposition that the expectations-augmented, long-run Phillips Curve is vertical (including some of the comments on my recent posts) suggest that people are not clear on what “long-run” means in the context of the expectations-augmented Phillips Curve and have not really thought carefully about what empirical content is contained by the proposition that the expectations-augmented, long-run Phillips Curve is vertical.

Just to frame the discussion of the Phillips Curve, let’s talk about what the term “long-run” means in economics. What it certainly does not mean is an amount of calendar time, though I won’t deny that there are frequent attempts to correlate long-run with varying durations of calendar time. But all such attempts either completely misunderstand what the long-run actually represents, or they merely aim to provide the untutored with some illusion of concreteness in what is otherwise a completely abstract discussion. In fact, what “long run” connotes is simply a full transition from one equilibrium state to another in the context of a comparative-statics exercise.

If a change in some exogenous parameter is imposed on a pre-existing equilibrium, then the long-run represents the full transition to a new equilibrium in which all endogenous variables have fully adjusted to the parameter change. The short-run, then, refers to some intermediate adjustment to the parameter change in which some endogenous variables have been arbitrarily held fixed (presumably because of some possibly reasonable assumption that some variables are able to adjust more speedily than other variables to the posited parameter change).

Now the Phillips Curve that was discovered by A. W. Phillips in his original paper was a strictly empirical relation between observed (wage) inflation and observed unemployment. But the expectations-augmented long-run Phillips Curve is a theoretical construct. And what it represents is certainly not an observable relationship between inflation and unemployment; it rather is a locus of points of equilibrium, each point representing full adjustment of the labor market to a particular rate of inflation, where full adjustment means that the rate of inflation is fully anticipated by all economic agents in the model. So what the expectations-augmented, long-run Phillips Curve is telling us is that if we perform a series of comparative-statics exercises in which, starting from full equilibrium with the given rate of inflation fully expected, we impose on the system a parameter change in which the exogenously imposed rate of inflation is changed and deduce a new equilibrium in which the fully and universally expected rate of inflation equals the alternative exogenously imposed inflation parameter, the equilibrium rate of unemployment corresponding to the new inflation parameter will not differ from the equilibrium rate of unemployment corresponding to the original inflation parameter.

Notice, as well, that the expectations-augmented, long-run Phillips Curve is not saying that imposing a new rate of inflation on an actual economic system would lead to a new equilibrium in which there was no change in unemployment; it is merely comparing alternative equilibria of the same system with different exogenously imposed rates of inflation. To make a statement about the effect of a change in the rate of inflation on unemployment, one has to be able to specify an adjustment path in moving from one equilibrium to another. The comparative-statics method says nothing about the adjustment path; it simply compares two alternative equilibrium states and specifies the change in endogenous variable induced by the change in an exogenous parameter.

So the vertical shape of the expectations-augmented, long-run Phillips Curve tells us very little about how, in any given situation, a change in the rate of inflation would actually affect the rate of unemployment. Not only does the expectations-augmented long-run Phillips Curve fail to tell us how a real system starting from equilibrium would be affected by a change in the rate of inflation, the underlying comparative-statics exercise being unable to specify the adjustment path taken by a system once it departs from its original equilibrium state, the expectations augmented, long-run Phillips Curve is even less equipped to tell us about the adjustment to a change in the rate of inflation when a system is not even in equilibrium to begin with.

The entire discourse of the expectations-augmented, long-run Phillips Curve is completely divorced from the kinds of questions that policy makers in the real world usually have to struggle with – questions like will increasing the rate of inflation of an economy in which there is abnormally high unemployment facilitate or obstruct the adjustment process that takes the economy back to a more normal unemployment rate. The expectations-augmented, long-run Phillips Curve may not be completely irrelevant to the making of economic policy – it is good to know, for example, that if we are trying to figure out which time path of NGDP to aim for, there is no particular reason to think that a time path with a 10% rate of growth of NGDP would probably not generate a significantly lower rate of unemployment than a time path with a 5% rate of growth – but its relationship to reality is sufficiently tenuous that it is irrelevant to any discussion of policy alternatives for economies unless those economies are already close to being in equilibrium.

Did David Hume Discover the Vertical Phillips Curve?

In my previous post about Nick Rowe and Milton Friedman, I pointed out to Nick Rowe that Friedman (and Phelps) did not discover the argument that the long-run Phillips Curve, defined so that every rate of inflation is correctly expected, is vertical. The argument I suggested can be traced back at least to Hume. My claim on Hume’s behalf was based on my vague recollection that Hume distinguished between the effect of a high price level and a rising price level, a high price level having no effect on output and employment, while a rising price level increases output and employment.

Scott Sumner offered the following comment, leaving it as an exercise for the reader to figure out what he meant by “didn’t quite get there.”:

As you know Friedman is one of the few areas where we disagree. Here I’ll just address one point, the expectations augmented Phillips Curve. Although I love Hume, he didn’t quite get there, although he did discuss the simple Phillips Curve.

I wrote the following response to Scott referring to the quote that I was thinking of without quoting it verbatim (because I couldn’t remember where to find it):

There is a wonderful quote by Hume about how low prices or high prices are irrelevant to total output, profits and employment, but that unexpected increases in prices are a stimulus to profits, output, and employment. I’ll look for it, and post it.

Nick Rowe then obligingly provided the quotation I was thinking of (but not all of it):

Here, to my mind, is the “money quote” (pun not originally intended) from David Hume’s “Of Money”:

“From the whole of this reasoning we may conclude, that it is of no manner of consequence, with regard to the domestic happiness of a state, whether money be in a greater or less quantity. The good policy of the magistrate consists only in keeping it, if possible, still encreasing; because, by that means, he keeps alive a spirit of industry in the nation, and encreases the stock of labour, in which consists all real power and riches.”

The first sentence is fine. But the second sentence is very clearly a problem.

Was it Friedman who said “we have only advanced one derivative since Hume”?

OK, so let’s see the whole relevant quotation from Hume’s essay “Of Money.”

Accordingly we find, that, in every kingdom, into which money begins to flow in greater abundance than formerly, everything takes a new face: labour and industry gain life; the merchant becomes more enterprising, the manufacturer more diligent and skilful, and even the farmer follows his plough with greater alacrity and attention. This is not easily to be accounted for, if we consider only the influence which a greater abundance of coin has in the kingdom itself, by heightening the price of Commodities, and obliging everyone to pay a greater number of these little yellow or white pieces for everything he purchases. And as to foreign trade, it appears, that great plenty of money is rather disadvantageous, by raising the price of every kind of labour.

To account, then, for this phenomenon, we must consider, that though the high price of commodities be a necessary consequence of the encrease of gold and silver, yet it follows not immediately upon that encrease; but some time is required before the money circulates through the whole state, and makes its effect be felt on all ranks of people. At first, no alteration is perceived; by degrees the price rises, first of one commodity, then of another; till the whole at last reaches a just proportion with the new quantity of specie which is in the kingdom. In my opinion, it is only in this interval or intermediate situation, between the acquisition of money and rise of prices, that the encreasing quantity of gold and silver is favourable to industry. When any quantity of money is imported into a nation, it is not at first dispersed into many hands; but is confined to the coffers of a few persons, who immediately seek to employ it to advantage. Here are a set of manufacturers or merchants, we shall suppose, who have received returns of gold and silver for goods which they sent to CADIZ. They are thereby enabled to employ more workmen than formerly, who never dream of demanding higher wages, but are glad of employment from such good paymasters. If workmen become scarce, the manufacturer gives higher wages, but at first requires an encrease of labour; and this is willingly submitted to by the artisan, who can now eat and drink better, to compensate his additional toil and fatigue.

He carries his money to market, where he, finds everything at the same price as formerly, but returns with greater quantity and of better kinds, for the use of his family. The farmer and gardener, finding, that all their commodities are taken off, apply themselves with alacrity to the raising more; and at the same time can afford to take better and more cloths from their tradesmen, whose price is the same as formerly, and their industry only whetted by so much new gain. It is easy to trace the money in its progress through the whole commonwealth; where we shall find, that it must first quicken the diligence of every individual, before it encrease the price of labour. And that the specie may encrease to a considerable pitch, before it have this latter effect, appears, amongst other instances, from the frequent operations of the FRENCH king on the money; where it was always found, that the augmenting of the numerary value did not produce a proportional rise of the prices, at least for some time. In the last year of LOUIS XIV, money was raised three-sevenths, but prices augmented only one. Corn in FRANCE is now sold at the same price, or for the same number of livres, it was in 1683; though silver was then at 30 livres the mark, and is now at 50. Not to mention the great addition of gold and silver, which may have come into that kingdom since the former period.

From the whole of this reasoning we may conclude, that it is of no manner of consequence, with regard to the domestic happiness of a state, whether money be in a greater or less quantity. The good policy of the magistrate consists only in keeping it, if possible, still encreasing; because, by that means, he keeps alive a spirit of industry in the nation, and encreases the stock of labour, in which consists all real power and riches. A nation, whose money decreases, is actually, at that time, weaker and more miserable than another nation, which possesses no more money, but is on the encreasing hand. This will be easily accounted for, if we consider, that the alterations in the quantity of money, either on one side or the other, are not immediately attended with proportionable alterations in the price of commodities. There is always an interval before matters be adjusted to their new situation; and this interval is as pernicious to industry, when gold and silver are diminishing, as it is advantageous when these metals are encreasing. The workman has not the same employment from the manufacturer and merchant; though he pays the same price for everything in the market. The farmer cannot dispose of his corn and cattle; though he must pay the same rent to his landlord. The poverty, and beggary, and sloth, which must ensue, are easily foreseen.

So Hume understands that once-and-for-all increases in the stock of money and in the price level are neutral, and also that in the transition from one price level to another, there will be a transitory effect on output and employment. However, when he says that the good policy of the magistrate consists only in keeping it, if possible, still increasing; because, by that means, he keeps alive a spirit of industry in the nation, he seems to be suggesting that the long-run Phillips Curve is actually positively sloped, thus confirming Milton Friedman (and Nick Rowe and Scott Sumner) in saying that Hume was off by one derivative.

While I think that is a fair reading of Hume, it is not the only one, because Hume really was thinking in terms of price levels, not rates of inflation. The idea that a good magistrate would keep the stock of money increasing could not have meant that the rate of inflation would indefinitely continue at a particular rate, only that the temporary increase in the price level would be extended a while longer. So I don’t think that Hume would ever have imagined that there could be a steady predicted rate of inflation lasting for an indefinite period of time. If he could have imagined a steady rate of inflation, I think he would have understood the simple argument that, once expected, the steady rate of inflation would not permanently increase output and employment.

At any rate, even if Hume did not explicitly anticipate Friedman’s argument for a vertical long-run Phillips Curve, certainly there many economists before Friedman who did. I will quote just one example from a source (Hayek’s Constitution of Liberty) that predates Friedman by about eight years. There is every reason to think that Friedman was familiar with the source, Hayek having been Friedman’s colleague at the University of Chicago between 1950 and 1962. The following excerpt is from p. 331 of the 1960 edition.

Inflation at first merely produces conditions in which more people make profits and in which profits are generally larger than usual. Almost everything succeeds, there are hardly any failures. The fact that profits again and again prove to be greater than had been expected and that an unusual number of ventures turn out to be successful produces a general atmosphere favorable to risk-taking. Even those who would have been driven out of business without the windfalls caused by the unexpected general rise in prices are able to hold on and to keep their employees in the expectation that they will soon share in the general prosperity. This situation will last, however, only until people begin to expect prices to continue to rise at the same rate. Once they begin to count on prices being so many per cent higher in so many months’ time, they will bid up the prices of the factors of production which determine the costs to a level corresponding to the future prices they expect. If prices then rise no more than had been expected, profits will return to normal, and the proportion of those making a profit also will fall; and since, during the period of exceptionally large profits, many have held on who would otherwise have been forced to change the direction of their efforts, a higher proportion than usual will suffer losses.

The stimulating effect of inflation will thus operate only so long as it has not been foreseen; as soon as it comes to be foreseen, only its continuation at an increased rate will maintain the same degree of prosperity. If in such a situation price rose less than expected, the effect would be the same as that of unforeseen deflation. Even if they rose only as much as was generally expected, this would no longer provide the expectational stimulus but would lay bare the whole backlog of adjustments that had been postponed while the temporary stimulus lasted. In order for inflation to retain its initial stimulating effect, it would have to continue at a rate always faster than expected.

This was certainly not the first time that Hayek made the same argument. See his Studies in Philosophy Politics and Economics, p. 295-96 for a 1958 version of the argument. Is there any part of Friedman’s argument in his 1968 essay (“The Role of Monetary Policy“) not contained in the quote from Hayek? Nor is there anything to indicate that Hayek thought he was making an argument that was not already familiar. The logic is so obvious that it is actually pointless to look for someone who “discovered” it. If Friedman somehow gets credit for making the discovery, it is simply because he was the one who made the argument at just the moment when the rest of the profession happened to be paying attention.

Richard Lipsey and the Phillips Curve

Richard Lipsey has had an extraordinarily long and productive career as both an economic theorist and an empirical economist, making numerous important contributions in almost all branches of economics. (See, for example, the citation about Lipsey as a fellow of the Canadian Economics Association.) In addition, his many textbooks have been enormously influential in advocating that economists should strive to make their discipline empirically relevant by actually subjecting their theories to meaningful empirical tests in which refutation is a realistic possibility not just a sign that the researcher was insufficiently creative in theorizing or in performing the data analysis.

One of Lipsey’s most important early contributions was his 1960 paper on the Phillips Curve “The Relationship between Unemployment and the Rate of Change of Money Wages in the United Kingdom 1862-1957: A Further Analysis” in which he extended W A. Phillips’s original results, and he has continued to write about the Phillips Curve ever since. Lipsey, in line with his empiricist philosophical position, has consistently argued that a well-supported empirical relationship should not be dismissed simply because of a purely theoretical argument about how expectations are formed. In other words, the argument that adjustments in inflation expectations would cause the short-run Phillips curve relation captured by empirical estimates of the relationship between inflation and unemployment may well be valid (as was actually recognized early on by Samuelson and Solow in their famous paper suggesting that the Phillips Curve could be interpreted as a menu of alternative combinations of inflation and unemployment from which policy-makers could choose) in some general qualitative sense. But that does not mean that it had to be accepted as an undisputable axiom of economics that the long-run relationship between unemployment and inflation is necessarily vertical, as Friedman and Phelps and Lucas convinced most of the economics profession in the late 1960s and early 1970s.

A few months ago, Lipsey was kind enough to send me a draft of the paper that he presented at the annual meeting of the History of Economics Society; the paper is called “The Phillips Curve and the Tyranny of an Assumed Unique Macro Equilibrium.” Here is the abstract of the paper.

To make the argument that the behaviour of modern industrial economies since the 1990s is inconsistent with theories in which there is a unique ergodic macro equilibrium, the paper starts by reviewing both the early Keynesian theory in which there was no unique level of income to which the economy was inevitably drawn and the debate about the amount of demand pressure at which it was best of maintain the economy: high aggregate demand and some inflationary pressure or lower aggregate demand and a stable price level. It then covers the rise of the simple Phillips curve and its expectations-augmented version, which introduced into current macro theory a natural rate of unemployment (and its associated equilibrium level of national income). This rate was also a NAIRU, the only rate consistent with stable inflation. It is then argued that the current behaviour of many modern economies in which there is a credible policy to maintain a low and steady inflation rate is inconsistent with the existence of either a unique natural rate or a NAIRU but is consistent with evolutionary theory in which there is perpetual change driven by endogenous technological advance. Instead of a NAIRU evolutionary economies have a non-inflationary band of unemployment (a NAIBU) indicating a range of unemployment and income over with the inflation rate is stable. The paper concludes with the observation that the great pre-Phillips curve debates of the 1950s that assumed that there was a range within which the economy could be run with varying pressures of demand, and varying amounts of unemployment and inflationary pressure, were not as silly as they were made to seem when both Keynesian and New Classical economists accepted the assumption of a perfectly inelastic, long-run Phillips curve located at the unique equilibrium level of unemployment.

Back in January, I wrote a post about the Lucas Critique in which I pointed out that his “proof” that the Phillips Curve is vertical in his celebrated paper on econometric policy evaluation was no proof at all, but simply a very special example in which the only disequilibrium permitted in the model – a misperception of the future price level – would lead an econometrician to estimate a negatively sloped relation between inflation and employment even though under correct expectations of inflation the relationship would be vertical. Allowing for a wider range of behavioral responses, I suggested, might well change the relation between inflation and output even under correctly expected inflation. In his new paper, Lipsey correctly points out that Friedman and Phelps and Lucas, and subsequent New Classical and New Keynesian theoreticians, who have embraced the vertical Phillips Curve doctrine as an article of faith, are also assuming, based on essentially no evidence, that there is a unique macro equilibrium. But, there is very strong evidence to suggest that, in fact, any deviation from an initial equilibrium (or equilibrium time path) is likely to cause changes that, in and of themselves, cause a change in conditions that will propel the system toward a new and different equilibrium time path, rather than return to the time path the system had been moving along before it was disturbed. See my post of almost a year ago about a paper, “Does history matter?: Empirical analysis of evolutionary versus stationary equilibrium views of the economy,” by Carlaw and Lipsey.)

Lipsey concludes his paper with a quotation from his article “The Phillips Curve” published in the volume Famous Figures and Diagrams in Economics edited by Mark Blaug and Peter Lloyd.

Perhaps [then] Keynesians were too hasty in following the New Classical economists in accepting the view that follows from static [and all EWD] models that stable rates of wage and price inflation are poised on the razor’s edge of a unique NAIRU and its accompanying Y*. The alternative does not require a long term Phillips curve trade off, nor does it deny the possibility of accelerating inflations of the kind that have bedevilled many third world countries. It is merely states that industrialised economies with low expected inflation rates may be less precisely responsive than current theory assumes because they are subject to many lags and inertias, and are operating in an ever-changing and uncertain world of endogenous technological change, which has no unique long term static equilibrium. If so, the economy may not be similar to the smoothly functioning mechanical world of Newtonian mechanics but rather to the imperfectly evolving world of evolutionary biology. The Phillips relation then changes from being a precise curve to being a band within which various combinations of inflation and unemployment are possible but outside of which inflation tends to accelerate or decelerate. Perhaps then the great [pre-Phillips curve] debates of the 1940s and early 1950s that assumed that there was a range within which the economy could be run with varying pressures of demand, and varying amounts of unemployment and inflation[ary pressure], were not as silly as they were made to seem when both Keynesian and New Classical economists accepted the assumption of a perfectly inelastic, one-dimensional, long run Phillips curve located at a unique equilibrium Y* and NAIRU.”

Charles Goodhart on Nominal GDP Targeting

Charles Goodhart might just be the best all-around monetary economist in the world, having made impressive contributions to both monetary theory and the history of monetary theory, to monetary history, and the history of monetary institutions, especially of central banking, and to the theory and, in his capacity as chief economist of the Bank of England, practice of monetary policy. So whenever Goodhart offers his views on monetary policy, it is a good idea to pay close attention to what he says. But if there is anything to be learned from the history of economics (and I daresay the history of any scientific discipline), it is that nobody ever gets it right all the time. It’s nice to have a reputation, but sadly reputation provides no protection from error.

In response to the recent buzz about targeting nominal GDP, Goodhart, emeritus professor at the London School of Economics and an adviser to Morgan Stanley along with two Morgan Stanley economists, Jonathan Ashworth and Melanie Baker, just published a critique of a recent speech by Mark Carney, Governor-elect of the Bank of England, in which Carney seemed to endorse targeting the level of nominal GDP (hereinafter NGDPLT). (See also Marcus Nunes’s excellent post about Goodhart et al.) Goodhart et al. have two basic complaints about NGDPLT. The first one is that our choice of an initial target level (i.e., do we think that current NGDP is now at its target or away from its target and if so by how much) and of the prescribed growth in the target level over time would itself create destabilizing uncertainty in the process of changing to an NGDPLT monetary regime. The key distinction between a level target and a growth-rate target is that the former requires a subsequent compensatory adjustment for any deviation from the target while the latter requires no such adjustment for a deviation from the target. Because deviations will occur under any targeting regime, Goodhart et al. worry that the compensatory adjustments required by NGDPLT could trigger destabilizing gyrations in NGDP growth, especially if expectations, as they think likely, became unanchored.

This concern seems easily enough handled if the monetary authority is given say a 1-1.5% band around its actual target within which to operate. Inevitable variations around the target would not automatically require an immediate rapid compensatory adjustment. As long as the monetary authority remained tolerably close to its target, it would not be compelled to make a sharp policy adjustment. A good driver does not always drive down the middle of his side of the road, the driver uses all the space available to avoid having to make an abrupt changes in the direction in which the car is headed. The same principle would govern the decisions of a skillful monetary authority.

Another concern of Goodhart et al. is that the choice of the target growth rate of NGDP depends on how much real growth,we think the economy is capable of. If real growth of 3% a year is possible, then the corresponding NGDP level target depends on how much inflation policy makers believe necessary to achieve that real GDP growth rate. If the “correct” rate of inflation is about 2%, then the targeted level of NGDP should grow at 5% a year. But Goodhart et al. are worried that achievable growth may be declining. If so, NGDPLT at 5% a year will imply more than 2% annual inflation.

Effectively, any overestimation of the sustainable real rate of growth, and such overestimation is all too likely, could force an MPC [monetary policy committee], subject to a level nominal GDP target, to soon have to aim for a significantly higher rate of inflation. Is that really what is now wanted? Bring back the stagflation of the 1970s; all is forgiven?

With all due respect, I find this concern greatly overblown. Even if the expectation of 3% real growth is wildly optimistic, say 2% too high, a 5% NGDP growth path would imply only 4% inflation. That might be too high a rate for Goodhart’s taste, or mine for that matter, but it would be a far cry from the 1970s, when inflation was often in the double-digits. Paul Volcker achieved legendary status in the annals of central banking by bringing the US rate of inflation down to 3.5 to 4%, so one needs to maintain some sense of proportion in these discussions.

Finally, Goodhart et al. invoke the Phillips Curve.

[A]n NGDP target would appear to run counter to the previously accepted tenets of monetary theory. Perhaps the main claim of monetary economics, as persistently argued by Friedman, and the main reason for having an independent Central Bank, is that over the medium and longer term monetary forces influence only monetary variables. Other real (e.g. supply-side) factors determine growth; the long-run Phillips curve is vertical. Do those advocating a nominal GDP target now deny that? Do they really believe that faster inflation now will generate a faster, sustainable, medium- and longer-term growth rate?

While it is certainly undeniable that Friedman showed, as, in truth, many others had before him, that, for an economy in approximate full-employment equilibrium, increased inflation cannot permanently reduce unemployment, it is far from obvious (to indulge in bit of British understatement) that we are now in a state of full-employment equilibrium. If the economy is not now in full-employment equilibrium, the idea that monetary-neutrality propositions about money influencing only monetary, but not real, variables in the medium and longer term are of no relevance to policy. Those advocating a nominal GDP target need not deny that the long-run Phillips Curve is vertical, though, as I have argued previously (here, here, and here) the proposition that the long-run Phillips Curve is vertical is very far from being the natural law that Goodhart and many others seem to regard it as. And if Goodhart et al. believe that we in fact are in a state of full-employment equilibrium, then they ought to say so forthrightly, and they ought to make an argument to justify that far from obvious characterization of the current state of affairs.

Having said all that, I do have some sympathy with the following point made by Goodhart et al.

Given our uncertainty about sustainable growth, an NGDP target also has the obvious disadvantage that future certainty about inflation becomes much less than under an inflation (or price level) target. In order to estimate medium- and longer-term inflation rates, one has first to take some view about the likely sustainable trends in future real output. The latter is very difficult to do at the best of times, and the present is not the best of times. So shifting from an inflation to a nominal GDP growth target is likely to have the effect of raising uncertainty about future inflation and weakening the anchoring effect on expectations of the inflation target.

That is one reason why in my book Free Banking and Monetary Reform, I advocated Earl Thompson’s proposal for a labor standard aimed at stabilizing average wages (or, more precisely, average expected wages). But if you stabilize wages, and productivity is falling, then prices must rise. That’s just a matter of arithmetic. But there is no reason why the macroeconomically optimal rate of inflation should be invariant with respect to the rate of technological progress.

HT:  Bill Woolsey

The Lucas Critique Revisited

After writing my previous post, I reread Robert Lucas’s classic article “Econometric Policy Evaluation: A Critique,” surely one of the most influential economics articles of the last half century. While the main point of the article was not entirely original, as Lucas himself acknowledged in the article, so powerful was his explanation of the point that it soon came to be known simply as the Lucas Critique. The Lucas Critique says that if a certain relationship between two economic variables has been estimated econometrically, policy makers, in formulating a policy for the future, cannot rely on that relationship to persist once a policy aiming to exploit the relationship is adopted. The motivation for the Lucas Critique was the Friedman-Phelps argument that a policy of inflation would fail to reduce the unemployment rate in the long run, because workers would eventually adjust their expectations of inflation, thereby draining inflation of any stimulative effect. By restating the Friedman-Phelps argument as the application of a more general principle, Lucas reinforced and solidified the natural-rate hypothesis, thereby establishing a key principle of modern macroeconomics.

In my previous post I argued that microeconomic relationships, e.g., demand curves and marginal rates of substitution, are, as a matter of pure theory, not independent of the state of the macroeconomy. In an interdependent economy all variables are mutually determined, so there is no warrant for saying that microrelationships are logically prior to, or even independent of, macrorelationships. If so, then the idea of microfoundations for macroeconomics is misleading, because all economic relationships are mutually interdependent; some relationships are not more basic or more fundamental than others. The kernel of truth in the idea of microfoundations is that there are certain basic principles or axioms of behavior that we don’t think an economic model should contradict, e.g., arbitrage opportunities should not be left unexploited – people should not pass up obvious opportunities, such as mutually beneficial offers of exchange, to increase their wealth or otherwise improve their state of well-being.

So I was curious to how see whether Lucas, while addressing the issue of how price expectations affected output and employment, recognized the possibility that a microeconomic relationship could be dependent on the state of the macroeconomy. For my purposes, the relevant passage occurs in section 5.3 (subtitled “Phillips Curves”) of the paper. After working out the basic theory earlier in the page, Lucas, in section 5, provided three examples of how econometric estimates of macroeconomic relationships would mislead policy makers if the effect of expectations on those relationships were not taken into account. The first two subsections treated consumption expenditures and the investment tax credit. The passage that I want to focus on consists of the first two paragraphs of subsection 5.3 (which I now quote verbatim except for minor changes in Lucas’s notation).

A third example is suggested by the recent controversy over the Phelps-Friedman hypothesis that permanent changes in the inflation rate will not alter the average rate of unemployment. Most of the major econometric models have been used in simulation experiments to test this proposition; the results are uniformly negative. Since expectations are involved in an essential way in labor and product market supply behavior, one would presumed, on the basis of the considerations raised in section 4, that these tests are beside the point. This presumption is correct, as the following example illustrates.

It will be helpful to utilize a simple, parametric model which captures the main features of the expectational view of aggregate supply – rational agents, cleared markets, incomplete information. We imagine suppliers of goods to be distributed over N distinct markets i, I = 1, . . ., N. To avoid index number problems, suppose that the same (except for location) good is traded in each market, and let y_it be the log of quantity supplied in market i in period t. Assume, further, that the supply y_it is composed of two factors

y_it = Py_it + Cy_it,

where Py_it denotes normal or permanent supply, and Cy_it cyclical or transitory supply (both again in logs). We take Py_it to be unresponsive to all but permanent relative price changes or, since the latter have been defined away by assuming a single good, simply unresponsive to price changes. Transitory supply Cy_it varies with perceived changes in the relative price of goods in i:

Cy_it = β(p_it – Ep_it),

where p_it is the log of the actual price in i at time t, and Ep_it is the log of the general (geometric average) price level in the economy as a whole, as perceived in market i.

Let’s take a moment to ponder the meaning of Lucas’s simplifying assumption that there is just one good. Relative prices (except for spatial differences in an otherwise identical good) are fixed by assumption; a disequilibrium (or suboptimal outcome) can arise only because of misperceptions of the aggregate price level. So, by explicit assumption, Lucas rules out the possibility that any microeconomic relationship depends on macroeconomic conditions. Note also that Lucas does not provide an account of the process by which market prices are established at each location, nothing being said about demand conditions. For example, if suppliers at location i perceive a price (transitorily) above the equilibrium price, and respond by (mistakenly) increasing output, thereby increasing their earnings, do those suppliers increase their demand to consume output? Suppose suppliers live and purchase at locations other than where they are supplying product, so that a supplier at location i purchases at location j, where i does not equal j. If a supplier at location i perceives an increase in price at location i, will his demand to purchase the good at location j increase as well? Will the increase in demand at location j cause an increase in the price at location j? What if there is a one-period lag between supplier receipts and their consumption demands? Lucas provides no insight into these possible ambiguities in his model.

Stated more generally, the problem with Lucas’s example is that it seems to be designed to exclude a priori the possibility of every type of disequilibrium but one, a disequilibrium corresponding to a single type of informational imperfection. Reasoning on the basis of that narrow premise, Lucas shows that, under a given expectation of the future price level, an econometrician would find a positive correlation between the price level and output — a negatively sloped Phillips Curve. Yet, under the same assumptions, Lucas also shows that an anticipated policy to raise the rate of inflation would fail to raise output (or, by implication, increase employment). But, given his very narrow underlying assumptions, it seems plausible to doubt the robustness of Lucas’s conclusion. Proving the validity of a proposition requires more than constructing an example in which the proposition is shown to be valid. That would be like trying to prove that the sides of every triangle are equal in length by constructing a triangle whose angles are all equal to 60 degrees, and then claiming that, because the sides of that triangle are equal in length, the sides of all triangles are equal in length.

Perhaps a better model than the one Lucas posited would have been one in which the amount supplied in each market was positively correlated with the amount supplied in every other market, inasmuch as an increase (decrease) in the amount supplied in one market will tend to increase (decrease) demand in other markets. In that case, I conjecture, deviations from permanent supply would tend to be cumulative (though not necessarily permanent), implying a more complex propagation mechanism than Lucas’s simple model does. Nor is it obvious to me how the equilibrium of such a model would compare to the equilibrium in the Lucas model. It does not seem inconceivable that a model could be constructed in which equilibrium output depended on the average price level. But this is just conjecture on my part, because I haven’t tried to write out and solve such a model. Perhaps an interested reader out there will try to work it out and report back to us on the results.

PS:  Congratulations to Scott Sumner on his excellent op-ed on nominal GDP level targeting in today’s Financial Times.

About Me

David Glasner
Washington, DC

I am an economist at the Federal Trade Commission. Nothing that you read on this blog necessarily reflects the views of the FTC or the individual commissioners. Although I work at the FTC as an antitrust economist, most of my research and writing has been on monetary economics and policy and the history of monetary theory. 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.

Enter your email address to follow this blog and receive notifications of new posts by email.

Join 374 other followers


Get every new post delivered to your Inbox.

Join 374 other followers