Archive for the 'microfoundations' Category



Franklin Fisher on the Stability(?) of General Equilibrium

The eminent Franklin Fisher, winner of the J. B. Clark Medal in 1973, a famed econometrician and antitrust economist, who was the expert economics witness for IBM in its long battle with the U. S. Department of Justice, and was later the expert witness for the Justice Department in the antitrust case against Microsoft, currently emeritus professor professor of microeconomics at MIT, visited the FTC today to give a talk about proposals the efficient sharing of water between Israel, Palestine, and Jordan. The talk was interesting and informative, but I must admit that I was more interested in Fisher’s views on the stability of general equilibrium, the subject of a monograph he wrote for the econometric society Disequilibrium Foundations of Equilibrium Economics, a book which I have not yet read, but hope to read before very long.

However, I did find a short paper by Fisher, “The Stability of General Equilibrium – What Do We Know and Why Is It Important?” (available here) which was included in a volume General Equilibrium Analysis: A Century after Walras edited by Pacal Bridel.

Fisher’s contribution was to show that the early stability analyses of general equilibrium, despite the efforts of some of the most best economists of the mid-twentieth century, e.g, Hicks, Samuelson, Arrow and Hurwicz (all Nobel Prize winners) failed to provide a useful analysis of the question whether the general equilibrium described by Walras, whose existence was first demonstrated under very restrictive assumptions by Abraham Wald, and later under more general conditions by Arrow and Debreu, is stable or not.

Although we routinely apply comparative-statics exercises to derive what Samuelson mislabeled “meaningful theorems,” meaning refutable propositions about the directional effects of a parameter change on some observable economic variable(s), such as the effect of an excise tax on the price and quantity sold of the taxed commodity, those comparative-statics exercises are predicated on the assumption that the exercise starts from an initial position of equilibrium and that the parameter change leads, in a short period of time, to a new equilibrium. But there is no theory describing the laws of motion leading from one equilibrium to another, so the whole exercise is built on the mere assumption that a general equilibrium is sufficiently stable so that the old and the new equilibria can be usefully compared. In other words, microeconomics is predicated on macroeconomic foundations, i.e., the stability of a general equilibrium. The methodological demand for microfoundations for macroeconomics is thus a massive and transparent exercise in question begging.

In his paper on the stability of general equilibrium, Fisher observes that there are four important issues to be explored by general-equilibrium theory: existence, uniqueness, optimality, and stability. Of these he considers optimality to be the most important, as it provides a justification for a capitalistic market economy. Fisher continues:

So elegant and powerful are these results, that most economists base their conclusions upon them and work in an equilibrium framework – as they do in partial equilibrium analysis. But the justification for so doing depends on the answer to the fourth question listed above, that of stability, and a favorable answer to that is by no means assured.

It is important to understand this point which is generally ignored by economists. No matter how desirable points of competitive general equilibrium may be, that is of no consequence if they cannot be reached fairly quickly or maintained thereafter, or, as might happen when a country decides to adopt free markets, there are bad consequences on the way to equilibrium.

Milton Friedman remarked to me long ago that the study of the stability of general equilibrium is unimportant, first, because it is obvious that the economy is stable, and, second, because if it isn’t stable we are wasting our time. He should have known better. In the first place, it is not at all obvious that the actual economy is stable. Apart from the lessons of the past few years, there is the fact that prices do change all the time. Beyond this, however, is a subtler and possibly more important point. Whether or not the actual economy is stable, we largely lack a convincing theory of why that should be so. Lacking such a theory, we do not have an adequate theory of value, and there is an important lacuna in the center of microeconomic theory.

Yet economists generally behave as though this problem did not exist. Perhaps the most extreme example of this is the view of the theory of Rational Expectations that any disequilibrium disappears so fast that it can be ignored. (If the 50-dollar bill were really on the sidewalk, it would be gone already.) But this simply assumes the problem away. The pursuit of profits is a major dynamic force in the competitive economy. To only look at situations where the Invisible Hand has finished its work cannot lead to a real understanding of how that work is accomplished. (p. 35)

I would also note that Fisher confirms a proposition that I have advanced a couple of times previously, namely that Walras’s Law is not generally valid except in a full general equilibrium with either a complete set of markets or correct price expectations. Outside of general equilibrium, Walras’s Law is valid only if trading is not permitted at disequilibrium prices, i.e., Walrasian tatonnement. Here’s how Fisher puts it.

In this context, it is appropriate to remark that Walras’s Law no longer holds in its original form. Instead of the sum of the money value of all excess demands over all agents being zero, it now turned out that, at any moment of time, the same sum (including the demands for shares of firms and for money) equals the difference between the total amount of dividends that households expect to receive at that time and the amount that firms expect to pay. This difference disappears in equilibrium where expectations are correct, and the classic version of Walras’s Law then holds.

Advertisements

Explaining the Hegemony of New Classical Economics

Simon Wren-Lewis, Robert Waldmann, and Paul Krugman have all recently devoted additional space to explaining – ruefully, for the most part – how it came about that New Classical Economics took over mainstream macroeconomics just about half a century after the Keynesian Revolution. And Mark Thoma got them all started by a complaint about the sorry state of modern macroeconomics and its failure to prevent or to cure the Little Depression.

Wren-Lewis believes that the main problem with modern macro is too much of a good thing, the good thing being microfoundations. Those microfoundations, in Wren-Lewis’s rendering, filled certain gaps in the ad hoc Keynesian expenditure functions. Although the gaps were not as serious as the New Classical School believed, adding an explicit model of intertemporal expenditure plans derived from optimization conditions and rational expectations, was, in Wren-Lewis’s estimation, an improvement on the old Keynesian theory. The improvements could have been easily assimilated into the old Keynesian theory, but weren’t because New Classicals wanted to junk, not improve, the received Keynesian theory.

Wren-Lewis believes that it is actually possible for the progeny of Keynes and the progeny of Fisher to coexist harmoniously, and despite his discomfort with the anti-Keynesian bias of modern macroeconomics, he views the current macroeconomic research program as progressive. By progressive, I interpret him to mean that macroeconomics is still generating new theoretical problems to investigate, and that attempts to solve those problems are producing a stream of interesting and useful publications – interesting and useful, that is, to other economists doing macroeconomic research. Whether the problems and their solutions are useful to anyone else is perhaps not quite so clear. But even if interest in modern macroeconomics is largely confined to practitioners of modern macroeconomics, that fact alone would not conclusively show that the research program in which they are engaged is not progressive, the progressiveness of the research program requiring no more than a sufficient number of self-selecting econ grad students, and a willingness of university departments and sources of research funding to cater to the idiosyncratic tastes of modern macroeconomists.

Robert Waldmann, unsurprisingly, takes a rather less charitable view of modern macroeconomics, focusing on its failure to discover any new, previously unknown, empirical facts about macroeconomic, or to better explain known facts than do alternative models, e.g., by more accurately predicting observed macro time-series data. By that, admittedly, demanding criterion, Waldmann finds nothing progressive in the modern macroeconomics research program.

Paul Krugman weighed in by emphasizing not only the ideological agenda behind the New Classical Revolution, but the self-interest of those involved:

Well, while the explicit message of such manifestos is intellectual – this is the only valid way to do macroeconomics – there’s also an implicit message: from now on, only my students and disciples will get jobs at good schools and publish in major journals/ And that, to an important extent, is exactly what happened; Ken Rogoff wrote about the “scars of not being able to publish stick-price papers during the years of new classical repression.” As time went on and members of the clique made up an ever-growing share of senior faculty and journal editors, the clique’s dominance became self-perpetuating – and impervious to intellectual failure.

I don’t disagree that there has been intellectual repression, and that this has made professional advancement difficult for those who don’t subscribe to the reigning macroeconomic orthodoxy, but I think that the story is more complicated than Krugman suggests. The reason I say that is because I cannot believe that the top-ranking economics departments at schools like MIT, Harvard, UC Berkeley, Princeton, and Penn, and other supposed bastions of saltwater thinking have bought into the underlying New Classical ideology. Nevertheless, microfounded DSGE models have become de rigueur for any serious academic macroeconomic theorizing, not only in the Journal of Political Economy (Chicago), but in the Quarterly Journal of Economics (Harvard), the Review of Economics and Statistics (MIT), and the American Economic Review. New Keynesians, like Simon Wren-Lewis, have made their peace with the new order, and old Keynesians have been relegated to the periphery, unable to publish in the journals that matter without observing the generally accepted (even by those who don’t subscribe to New Classical ideology) conventions of proper macroeconomic discourse.

So I don’t think that Krugman’s ideology plus self-interest story fully explains how the New Classical hegemony was achieved. What I think is missing from his story is the spurious methodological requirement of microfoundations foisted on macroeconomists in the course of the 1970s. I have discussed microfoundations in a number of earlier posts (here, here, here, here, and here) so I will try, possibly in vain, not to repeat myself too much.

The importance and desirability of microfoundations were never questioned. What, after all, was the neoclassical synthesis, if not an attempt, partly successful and partly unsuccessful, to integrate monetary theory with value theory, or macroeconomics with microeconomics? But in the early 1970s the focus of attempts, notably in the 1970 Phelps volume, to provide microfoundations changed from embedding the Keynesian system in a general-equilibrium framework, as Patinkin had done, to providing an explicit microeconomic rationale for the Keynesian idea that the labor market could not be cleared via wage adjustments.

In chapter 19 of the General Theory, Keynes struggled to come up with a convincing general explanation for the failure of nominal-wage reductions to clear the labor market. Instead, he offered an assortment of seemingly ad hoc arguments about why nominal-wage adjustments would not succeed in reducing unemployment, enabling all workers willing to work at the prevailing wage to find employment at that wage. This forced Keynesians into the awkward position of relying on an argument — wages tend to be sticky, especially in the downward direction — that was not really different from one used by the “Classical Economists” excoriated by Keynes to explain high unemployment: that rigidities in the price system – often politically imposed rigidities – prevented wage and price adjustments from equilibrating demand with supply in the textbook fashion.

These early attempts at providing microfoundations were largely exercises in applied price theory, explaining why self-interested behavior by rational workers and employers lacking perfect information about all potential jobs and all potential workers would not result in immediate price adjustments that would enable all workers to find employment at a uniform market-clearing wage. Although these largely search-theoretic models led to a more sophisticated and nuanced understanding of labor-market dynamics than economists had previously had, the models ultimately did not provide a fully satisfactory account of cyclical unemployment. But the goal of microfoundations was to explain a certain set of phenomena in the labor market that had not been seriously investigated, in the hope that price and wage stickiness could be analyzed as an economic phenomenon rather than being arbitrarily introduced into models as an ad hoc, albeit seemingly plausible, assumption.

But instead of pursuing microfoundations as an explanatory strategy, the New Classicals chose to impose it as a methodological prerequisite. A macroeconomic model was inadmissible unless it could be explicitly and formally derived from the optimizing choices of fully rational agents. Instead of trying to enrich and potentially transform the Keynesian model with a deeper analysis and understanding of the incentives and constraints under which workers and employers make decisions, the New Classicals used microfoundations as a methodological tool by which to delegitimize Keynesian models, those models being insufficiently or improperly microfounded. Instead of using microfoundations as a method by which to make macroeconomic models conform more closely to the imperfect and limited informational resources available to actual employers deciding to hire or fire employees, and actual workers deciding to accept or reject employment opportunities, the New Classicals chose to use microfoundations as a methodological justification for the extreme unrealism of the rational-expectations assumption, portraying it as nothing more than the consistent application of the rationality postulate underlying standard neoclassical price theory.

For the New Classicals, microfoundations became a reductionist crusade. There is only one kind of economics, and it is not macroeconomics. Even the idea that there could be a conceptual distinction between micro and macroeconomics was unacceptable to Robert Lucas, just as the idea that there is, or could be, a mind not reducible to the brain is unacceptable to some deranged neuroscientists. No science, not even chemistry, has been reduced to physics. Were it ever to be accomplished, the reduction of chemistry to physics would be a great scientific achievement. Some parts of chemistry have been reduced to physics, which is a good thing, especially when doing so actually enhances our understanding of the chemical process and results in an improved, or more exact, restatement of the relevant chemical laws. But it would be absurd and preposterous simply to reject, on supposed methodological principle, those parts of chemistry that have not been reduced to physics. And how much more absurd would it be to reject higher-level sciences, like biology and ecology, for no other reason than that they have not been reduced to physics.

But reductionism is what modern macroeconomics, under the New Classical hegemony, insists on. No exceptions allowed; don’t even ask. Meekly and unreflectively, modern macroeconomics has succumbed to the absurd and arrogant methodological authoritarianism of the New Classical Revolution. What an embarrassment.

UPDATE (11:43 AM EDST): I made some minor editorial revisions to eliminate some grammatical errors and misplaced or superfluous words.

Methodological Arrogance

A few weeks ago, I posted a somewhat critical review of Kartik Athreya’s new book Big Ideas in Macroeconomics. In quoting a passage from chapter 4 in which Kartik defended the rational-expectations axiom on the grounds that it protects the public from economists who, if left unconstrained by the discipline of rational expectations, could use expectational assumptions to generate whatever results they wanted, I suggested that this sort of reasoning in defense of the rational-expectations axiom betrayed what I called the “methodological arrogance” of modern macroeconomics which has, to a large extent, succeeded in imposing that axiom on all macroeconomic models. In his comment responding to my criticisms, Kartik made good-natured reference in passing to my charge of “methodological arrogance,” without substantively engaging with the charge. And in a post about the early reviews of Kartik’s book, Steve Williamson, while crediting me for at least reading the book before commenting on it, registered puzzlement at what I meant by “methodological arrogance.”

Actually, I realized when writing that post that I was not being entirely clear about what “methodological arrogance” meant, but I thought that my somewhat tongue-in-cheek reference to the duty of modern macroeconomists “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” was sufficiently suggestive not to require elaboration, especially after having devoted several earlier posts to criticisms of the methodology of modern macroeconomics (e.g., here, here, and here). That was a misjudgment.

So let me try to explain what I mean by methodological arrogance, which is not the quite the same as, but is closely related to, methodological authoritarianism. I will do so by referring to the long introductory essay (“A Realist View of Logic, Physics, and History”) that Karl Popper contributed to a book The Self and Its Brain co-authored with neuroscientist John Eccles. The chief aim of the essay was to argue that the universe is not fully determined, but evolves, producing new, emergent, phenomena not originally extant in the universe, such as the higher elements, life, consciousness, language, science and all other products of human creativity, which in turn interact with the universe, in fundamentally unpredictable ways. Popper regards consciousness as a real phenomenon that cannot be reduced to or explained by purely physical causes. Though he makes only brief passing reference to the social sciences, Popper’s criticisms of reductionism are directly applicable to the microfoundations program of modern macroeconomics, and so I think it will be useful to quote what he wrote at some length.

Against the acceptance of the view of emergent evolution there is a strong intuitive prejudice. It is the intuition that, if the universe consists of atoms or elementary particles, so that all things are structures of such particles, then every event in the universe ought to be explicable, and in principle predictable, in terms of particle structure and of particle interaction.

Notice how easy it would be rephrase this statement as a statement about microfoundations:

Against the acceptance of the view that there are macroeconomic phenomena, there is a strong intuitive prejudice. It is the intuition that, if the macroeconomy consists of independent agents, so that all macroeconomic phenomena are the result of decisions made by independent agents, then every macreconomic event ought to be explicable, and in principle predictable, in terms of the decisions of individual agents and their interactions.

Popper continues:

Thus we are led to what has been called the programme of reductionism [microfoundations]. In order to discuss it I shall make use of the following Table

(12) Level of ecosystems

(11) Level of populations of metazoan and plants

(10) Level of metezoa and multicellular plants

(9) Level of tissues and organs (and of sponges?)

(8) Level of populations of unicellular organisms

(7) Level of cells and of unicellular organisms

(6) Level of organelles (and perhaps of viruses)

(5) Liquids and solids (crystals)

(4) Molecules

(3) Atoms

(2) Elementary particles

(1) Sub-elementary particles

(0) Unknown sub-sub-elementary particles?

The reductionist idea behind this table is that the events or things on each level should be explained in terms of the lower levels. . . .

This reductionist idea is interesting and important; and whenever we can explain entities and events on a higher level by those of a lower level, we can speak of a great scientific success, and can say that we have added much to our understanding of the higher level. As a research programme, reductionism is not only important, but it is part of the programme of science whose aim is to explain and to understand.

So far so good. Reductionism certainly has its place. So do microfoundations. Whenever we can take an observation and explain it in terms of its constituent elements, we have accomplished something important. We have made scientific progress.

But Popper goes on to voice a cautionary note. There may be, and probably are, strict, perhaps insuperable, limits to how far higher-level phenomena can be reduced to (explained by) lower-level phenomena.

[E]ven the often referred to reduction of chemistry to physics, important as it is, is far from complete, and very possibly incompletable. . . . [W]e are far removed indeed from being able to claim that all, or most, properties of chemical compounds can be reduced to atomic theory. . . . In fact, the five lower levels of [our] Table . . . can be used to show that we have reason to regard this kind of intuitive reduction programme as clashing with some results of modern physics.

For what [our] Table suggests may be characterized as the principle of “upward causation.” This is the principle that causation can be traced in our Table . . . . from a lower level to a higher level, but not vice versa; that what happens on a higher level can be explained in terms of the next lower level, and ultimately in terms of elementary particles and the relevant physical laws. It appears at first that the higher levels cannot act on the lower ones.

But the idea of particle-to-particle or atom-to-atom interaction has been superseded by physics itself. A diffraction grating or a crystal (belonging to level (5) of our Table . . .) is a spatially very extended complex (and periodic) structure of billions of molecules; but it interacts as a whole extended periodic structure with the photons or the particles of a beam of photons or particles. Thus we have here an important example of “downward causation“. . . . That is to say, the whole, the macro structure, may, qua whole, act upon a photon or an elementary particle or an atom. . . .

Other physical examples of downward causation – of macroscopic structures on level (5) acting upon elementary particles or photons on level (1) – are lasers, masers, and holograms. And there are also many other macro structures which are examples of downward causation: every simple arrangement of negative feedback, such as a steam engine governor, is a macroscopic structure that regulates lower level events, such as the flow of the molecules that constitute the steam. Downward causation is of course important in all tools and machines which are designed for sompe purpose. When we use a wedge, for example, we do not arrange for the action of its elementary particles, but we use a structure, relying on it ot guide the actions of its constituent elementary particles to act, in concert, so as to achieve the desired result.

Stars are undersigned, but one may look at them as undersigned “machines” for putting the atoms and elementary particles in their central region under terrific gravitational pressure, with the (undersigned) result that some atomic nuclei fuse and form the nuclei of heavier elements; an excellent example of downward causation,of the action of the whole structure upon its constituent particles.

(Stars, incidentally, are good examples of the general rule that things are processes. Also, they illustrate the mistake of distinguishing between “wholes” – which are “more than the sums of their parts” – and “mere heaps”: a star is, in a sense, a “mere” accumulation, a “mere heap” of its constituent atoms. Yet it is a process – a dynamic structure. Its stability depends upon the dynamic equilibrium between its gravitational pressure, due to its sheer bulk, and the repulsive forces between its closely packed elementary particles. If the latter are excessive, the star explodes, If they are smaller than the gravitational pressure, it collapses into a “black hole.”

The most interesting examples of downward causation are to be found in organisms and in their ecological systems, and in societies of organisms [my emphasis]. A society may continue to function even though many of its members die; but a strike in an essential industry, such as the supply of electricity, may cause great suffering to many individual people. .. . I believe that these examples make the existence of downward causation obvious; and they make the complete success of any reductionist programme at least problematic.

I was very glad when I recently found this discussion of reductionism by Popper in a book that I had not opened for maybe 40 years, because it supports an argument that I have been making on this blog against the microfoundations program in macroeconomics: that as much as macroeconomics requires microfoundations, microeconomics also requires macrofoundations. Here is how I put a little over a year ago:

In fact, the standard comparative-statics propositions of microeconomics are also based on the assumption of the existence of a unique stable general equilibrium. Those comparative-statics propositions about the signs of the derivatives of various endogenous variables (price, quantity demanded, quantity supplied, etc.) with respect to various parameters of a microeconomic model involve comparisons between equilibrium values of the relevant variables before and after the posited parametric changes. All such comparative-statics results involve a ceteris-paribus assumption, conditional on the existence of a unique stable general equilibrium which serves as the starting and ending point (after adjustment to the parameter change) of the exercise, thereby isolating the purely hypothetical effect of a parameter change. Thus, as much as macroeconomics may require microfoundations, microeconomics is no less in need of macrofoundations, i.e., the existence of a unique stable general equilibrium, absent which a comparative-statics exercise would be meaningless, because the ceteris-paribus assumption could not otherwise be maintained. To assert that macroeconomics is impossible without microfoundations is therefore to reason in a circle, the empirically relevant propositions of microeconomics being predicated on the existence of a unique stable general equilibrium. But it is precisely the putative failure of a unique stable intertemporal general equilibrium to be attained, or to serve as a powerful attractor to economic variables, that provides the rationale for the existence of a field called macroeconomics.

And more recently, I put it this way:

The microeconomic theory of price adjustment is a theory of price adjustment in a single market. It is a theory in which, implicitly, all prices and quantities, but a single price-quantity pair are in equilibrium. Equilibrium in that single market is rapidly restored by price and quantity adjustment in that single market. That is why I have said that microeconomics rests on a macroeconomic foundation, and that is why it is illusory to imagine that macroeconomics can be logically derived from microfoundations. Microfoundations, insofar as they explain how prices adjust, are themselves founded on the existence of a macroeconomic equilibrium. Founding macroeconomics on microfoundations is just a form of bootstrapping.

So I think that my criticism of the microfoundations project exactly captures the gist of Popper’s criticism of reductionism. Popper extended his criticism of a certain form of reductionism, which he called “radical materialism or radical physicalism” in later passage in the same essay that is also worth quoting:

Radical materialism or radical physicalism is certainly a selfconsistent position. Fir it is a view of the universe which, as far as we know, was adequate once; that is, before the emergence of life and consciousness. . . .

What speaks in favour of radical materialism or radical physicalism is, of course, that it offers us a simple vision of a simple universe, and this looks attractive just because, in science, we search for simple theories. However, I think that it is important that we note that there are two different ways by which we can search for simplicity. They may be called, briefly, philosophical reduction and scientific reduction. The former is characterized by an attempt to provide bold and testable theories of high explanatory power. I believe that the latter is an extremely valuable and worthwhile method; while the former is of value only if we have good reasons to assume that it corresponds to the facts about the universe.

Indeed, the demand for simplicity in the sense of philosophical rather than scientific reduction may actually be damaging. For even in order to attempt scientific reduction, it is necessary for us to get a full grasp of the problem to be solved, and it is therefore vitally important that interesting problems are not “explained away” by philosophical analysis. If, say, more than one factor is responsible for some effect, it is important that we do not pre-empt the scientific judgment: there is always the danger that we might refuse to admit any ideas other than the ones we appear to have at hand: explaining away, or belittling the problem. The danger is increased if we try to settle the matter in advance by philosophical reduction. Philosophical reduction also makes us blind to the significance of scientific reduction.

Popper adds the following footnote about the difference between philosophic and scientific reduction.

Consider, for example, what a dogmatic philosophical reductionist of a mechanistic disposition (or even a quantum-mechanistic disposition) might have done in the face of the problem of the chemical bond. The actual reduction, so far as it goes, of the theory of the hydrogen bond to quantum mechanics is far more interesting than the philosophical assertion that such a reduction will one be achieved.

What modern macroeconomics now offers is largely an array of models simplified sufficiently so that they are solvable using the techniques of dynamic optimization. Dynamic optimization by individual agents — the microfoundations of modern macro — makes sense only in the context of an intertemporal equilibrium. But it is just the possibility that intertemporal equilibrium may not obtain that, to some of us at least, makes macroeconomics interesting and relevant. As the great Cambridge economist, Frederick Lavington, anticipating Popper in grasping the possibility of downward causation, put it so well, “the inactivity of all is the cause of the inactivity of each.”

So what do I mean by methodological arrogance? I mean an attitude that invokes microfoundations as a methodological principle — philosophical reductionism in Popper’s terminology — while dismissing non-microfounded macromodels as unscientific. To be sure, the progress of science may enable us to reformulate (and perhaps improve) explanations of certain higher-level phenomena by expressing those relationships in terms of lower-level concepts. That is what Popper calls scientific reduction. But scientific reduction is very different from rejecting, on methodological principle, any explanation not expressed in terms of more basic concepts.

And whenever macrotheory seems inconsistent with microtheory, the inconsistency poses a problem to be solved. Solving the problem will advance our understanding. But simply to reject the macrotheory on methodological principle without evidence that the microfounded theory gives a better explanation of the observed phenomena than the non-microfounded macrotheory (and especially when the evidence strongly indicates the opposite) is arrogant. Microfoundations for macroeconomics should result from progress in economic theory, not from a dubious methodological precept.

Let me quote Popper again (this time from his book Objective Knowledge) about the difference between scientific and philosophical reduction, addressing the denial by physicalists that that there is such a thing as consciousness, a denial based on their belief that all supposedly mental phenomena can and will ultimately be reduced to purely physical phenomena

[P]hilosophical speculations of a materialistic or physicalistic character are very interesting, and may even be able to point the way to a successful scientific reduction. But they should be frankly tentative theories. . . . Some physicalists do not, however, consider their theories as tentative, but as proposals to express everything in physicalist language; and they think these proposals have much in their favour because they are undoubtedly convenient: inconvenient problems such as the body-mind problem do indeed, most conveniently, disappear. So these physicalists think that there can be no doubt that these problems should be eliminated as pseudo-problems. (p. 293)

One could easily substitute “methodological speculations about macroeconomics” for “philosophical speculations of a materialistic or physicalistic character” in the first sentence. And in the third sentence one could substitute “advocates of microfounding all macroeconomic theories” for “physicalists,” “microeconomic” for “physicalist,” and “Phillips Curve” or “involuntary unemployment” for “body-mind problem.”

So, yes, I think it is arrogant to think that you can settle an argument by forcing the other side to use only those terms that you approve of.

What Does “Keynesian” Mean?

Last week Simon Wren-Lewis wrote a really interesting post on his blog trying to find the right labels with which to identify macroeconomists. Simon, rather disarmingly, starts by admitting the ultimate futility of assigning people labels; reality is just too complicated to conform to the labels that we invent to help ourselves make sense of reality. A good label can provide us with a handle with which to gain a better grasp on a messy set of observations, but it is not the reality. And if you come up with one label, I may counter with a different one. Who’s to say which label is better?

At any rate, as I read through Simon’s post I found myself alternately nodding my head in agreement and shaking my head in disagreement. So staying in the spirit of fun in which Simon wrote his post, I will provide a commentary on his labels and other pronouncements. If the comments are weighted on the side of disagreement, well, that’s what makes blogging fun, n’est-ce pas?

Simon divides academic researchers into two groups (mainstream and heterodox) and macroeconomic policy into two approaches (Keynesian and anti-Keynesian). He then offers the following comment on the meaning of the label Keynesian.

Just think about the label Keynesian. Any sensible definition would involve the words sticky prices and aggregate demand. Yet there are still some economists (generally not academics) who think Keynesian means believing fiscal rather than monetary policy should be used to stabilise demand. Fifty years ago maybe, but no longer. Even worse are non-economists who think being a Keynesian means believing in market imperfections, government intervention in general and a mixed economy. (If you do not believe this happens, look at the definition in Wikipedia.)

Well, as I pointed out in a recent post, there is nothing peculiarly Keynesian about the assumption of sticky prices, especially not as a necessary condition for an output gap and involuntary unemployment. So if Simon is going to have to work harder to justify his distinction between Keynesian and anti-Keynesian. In a comment on Simon’s blog, Nick Rowe pointed out just this problem, asking in particular why Simon could not substitute a Monetarist/anti-Monetarist dichotomy for the Keynesian/anti-Keynesian one.

The story gets more complicated in Simon’s next paragraph in which he describes his dichotomy of academic research into mainstream and heterodox.

Thanks to the microfoundations revolution in macro, mainstream macroeconomists speak the same language. I can go to a seminar that involves an RBC model with flexible prices and no involuntary unemployment and still contribute and possibly learn something. Equally an economist like John Cochrane can and does engage in meaningful discussions of New Keynesian theory (pdf).

In other words, the range of acceptable macroeconomic models has been drastically narrowed. Unless it is microfounded in a dynamic stochastic general equilibrium model, a model does not qualify as “mainstream.” This notion of microfoundation is certainly not what Edmund Phelps meant by “microeconomic foundations” when he edited his famous volume Microeconomic Foundations of Employment and Inflation Theory, which contained, among others, Alchian’s classic paper on search costs and unemployment and a paper by the then not so well-known Robert Lucas and his early collaborator Leonard Rapping. Nevertheless, in the current consensus, it is apparently the New Classicals that determine what kind of model is acceptable, while New Keynesians are allowed to make whatever adjustments, mainly sticky wages, they need to derive Keynesian policy recommendations. Anyone who doesn’t go along with this bargain is excluded from the mainstream. Simon may not be happy with this state of affairs, but he seems to have made peace with it without undue discomfort.

Now many mainstream macroeconomists, myself included, can be pretty critical of the limitations that this programme can place on economic thinking, particularly if it is taken too literally by microfoundations purists. But like it or not, that is how most macro research is done nowadays in the mainstream, and I see no sign of this changing anytime soon. (Paul Krugman discusses some reasons why here.) My own view is that I would like to see more tolerance and a greater variety of modelling approaches, but a pragmatic microfoundations macro will and should remain the major academic research paradigm.

Thus, within the mainstream, there is no basic difference in how to create a macroeconomic model. The difference is just in how to tweak the model in order to derive the desired policy implication.

When it comes to macroeconomic policy, and keeping to the different language idea, the only significant division I see is between the mainstream macro practiced by most economists, including those in most central banks, and anti-Keynesians. By anti-Keynesian I mean those who deny the potential for aggregate demand to influence output and unemployment in the short term.

So, even though New Keynesians have learned how to speak the language of New Classicals, New Keynesians can console themselves in retaining the upper hand in policy discussions. Which is why in policy terms, Simon chooses a label that is at least suggestive of a certain Keynesian primacy, the other side being defined in terms of their opposition to Keynesian policy. Half apologetically, Simon then asks: “Why do I use the term anti-Keynesian rather than, say, New Classical?” After all, it’s the New Classical model that’s being tweaked. Simon responds:

Partly because New Keynesian economics essentially just augments New Classical macroeconomics with sticky prices. But also because as far as I can see what holds anti-Keynesians together isn’t some coherent and realistic view of the world, but instead a dislike of what taking aggregate demand seriously implies.

This explanation really annoyed Steve Williamson who commented on Simon’s blog as follows:

Part of what defines a Keynesian (new or old), is that a Keynesian thinks that his or her views are “mainstream,” and that the rest of macroeconomic thought is defined relative to what Keynesians think – Keynesians reside at the center of the universe, and everything else revolves around them.

Simon goes on to explain what he means by the incoherence of the anti-Keynesian view of the world, pointing out that the Pigou Effect, which supposedly invalidated Keynes’s argument that perfect wage and price flexibility would not eventually restore full employment to an economy operating at less than full employment, has itself been shown not to be valid. And then Simon invokes that old standby Say’s Law.

Second, the evidence that prices are not flexible is so overwhelming that you need something else to drive you to ignore this evidence. Or to put it another way, you need something pretty strong for politicians or economists to make the ‘schoolboy error’ that is Says Law, which is why I think the basis of the anti-Keynesian view is essentially ideological.

Here, I think, Simon is missing something important. It was a mistake on Keynes’s part to focus on Say’s Law as the epitome of everything wrong with “classical economics.” Actually Say’s Law is a description of what happens in an economy when trading takes place at disequilibrium prices. At disequilibrium prices, potential gains from trade are left on the table. Not only are they left on the table, but the effects can be cumulative, because the failure to supply implies a further failure to demand. The Keynesian spending multiplier is the other side of the coin of the supply-side contraction envisioned by Say. Even infinite wage and price flexibility may not help an economy in which a lot of trade is occurring at disequilibrium prices.

The microeconomic theory of price adjustment is a theory of price adjustment in a single market. It is a theory in which, implicitly, all prices and quantities, but a single price-quantity pair are in equilibrium. Equilibrium in that single market is rapidly restored by price and quantity adjustment in that single market. That is why I have said that microeconomics rests on a macroeconomic foundation, and that is why it is illusory to imagine that macroeconomics can be logically derived from microfoundations. Microfoundations, insofar as they explain how prices adjust, are themselves founded on the existence of a macroeconomic equilibrium. Founding macroeconomics on microfoundations is just a form of bootstrapping.

If there is widespread unemployment, it may indeed be that wages are too high, and that a reduction in wages would restore equilibrium. But there is no general presumption that unemployment will be cured by a reduction in wages. Unemployment may be the result of a more general dysfunction in which all prices are away from their equilibrium levels, in which case no adjustment of the wage would solve the problem, so that there is no presumption that the current wage exceeds the full-equilibrium wage. This, by the way, seems to me to be nothing more than a straightforward implication of the Lipsey-Lancaster theory of second best.

Macroeconomic Science and Meaningful Theorems

Greg Hill has a terrific post on his blog, providing the coup de grace to Stephen Williamson’s attempt to show that the way to increase inflation is for the Fed to raise its Federal Funds rate target. Williamson’s problem, Hill points out is that he attempts to derive his results from relationships that exist in equilibrium. But equilibrium relationships in and of themselves are sterile. What we care about is how a system responds to some change that disturbs a pre-existing equilibrium.

Williamson acknowledged that “the stories about convergence to competitive equilibrium – the Walrasian auctioneer, learning – are indeed just stories . . . [they] come from outside the model” (here).  And, finally, this: “Telling stories outside of the model we have written down opens up the possibility for cheating. If everything is up front – written down in terms of explicit mathematics – then we have to be honest. We’re not doing critical theory here – we’re doing economics, and we want to be treated seriously by other scientists.”

This self-conscious scientism on Williamson’s part is not just annoyingly self-congratulatory. “Hey, look at me! I can write down mathematical models, so I’m a scientist, just like Richard Feynman.” It’s wildly inaccurate, because the mere statement of equilibrium conditions is theoretically vacuous. Back to Greg:

The most disconcerting thing about Professor Williamson’s justification of “scientific economics” isn’t its uncritical “scientism,” nor is it his defense of mathematical modeling. On the contrary, the most troubling thing is Williamson’s acknowledgement-cum-proclamation that his models, like many others, assume that markets are always in equilibrium.

Why is this assumption a problem?  Because, as Arrow, Debreu, and others demonstrated a half-century ago, the conditions required for general equilibrium are unimaginably stringent.  And no one who’s not already ensconced within Williamson’s camp is likely to characterize real-world economies as always being in equilibrium or quickly converging upon it.  Thus, when Williamson responds to a question about this point with, “Much of economics is competitive equilibrium, so if this is a problem for me, it’s a problem for most of the profession,” I’m inclined to reply, “Yes, Professor, that’s precisely the point!”

Greg proceeds to explain that the Walrasian general equilibrium model involves the critical assumption (implemented by the convenient fiction of an auctioneer who announces prices and computes supply and demand at that prices before allowing trade to take place) that no trading takes place except at the equilibrium price vector (where the number of elements in the vector equals the number of prices in the economy). Without an auctioneer there is no way to ensure that the equilibrium price vector, even if it exists, will ever be found.

Franklin Fisher has shown that decisions made out of equilibrium will only converge to equilibrium under highly restrictive conditions (in particular, “no favorable surprises,” i.e., all “sudden changes in expectations are disappointing”).  And since Fisher has, in fact, written down “the explicit mathematics” leading to this conclusion, mustn’t we conclude that the economists who assume that markets are always in equilibrium are really the ones who are “cheating”?

An alternative general equilibrium story is that learning takes place allowing the economy to converge on a general equilibrium time path over time, but Greg easily disposes of that story as well.

[T]he learning narrative also harbors massive problems, which come out clearly when viewed against the background of the Arrow-Debreu idealized general equilibrium construction, which includes a complete set of intertemporal markets in contingent claims.  In the world of Arrow-Debreu, every price in every possible state of nature is known at the moment when everyone’s once-and-for-all commitments are made.  Nature then unfolds – her succession of states is revealed – and resources are exchanged in accordance with the (contractual) commitments undertaken “at the beginning.”

In real-world economies, these intertemporal markets are woefully incomplete, so there’s trading at every date, and a “sequence economy” takes the place of Arrow and Debreu’s timeless general equilibrium.  In a sequence economy, buyers and sellers must act on their expectations of future events and the prices that will prevail in light of these outcomes.  In the limiting case of rational expectations, all agents correctly forecast the equilibrium prices associated with every possible state of nature, and no one’s expectations are disappointed. 

Unfortunately, the notion that rational expectations about future prices can replace the complete menu of Arrow-Debreu prices is hard to swallow.  Frank Hahn, who co-authored “General Competitive Analysis” with Kenneth Arrow (1972), could not begin to swallow it, and, in his disgorgement, proceeded to describe in excruciating detail why the assumption of rational expectations isn’t up to the job (here).  And incomplete markets are, of course, but one departure from Arrow-Debreu.  In fact, there are so many more that Hahn came to ridicule the approach of sweeping them all aside, and “simply supposing the economy to be in equilibrium at every moment of time.”

Just to pile on, I would also point out that any general equilibrium model assumes that there is a given state of knowledge that is available to all traders collectively, but not necessarily to each trader. In this context, learning means that traders gradually learn what the pre-existing facts are. But in the real world, knowledge increases and evolves through time. As knowledge changes, capital — both human and physical — embodying that knowledge becomes obsolete and has to be replaced or upgraded, at unpredictable moments of time, because it is the nature of new knowledge that it cannot be predicted. The concept of learning incorporated in these sorts of general equilibrium constructs is a travesty of the kind of learning that characterizes the growth of knowledge in the real world. The implications for the existence of a general equilibrium model in a world in which knowledge grows in an unpredictable way are devastating.

Greg aptly sums up the absurdity of using general equilibrium theory (the description of a decentralized economy in which the component parts are in a state of perfect coordination) as the microfoundation for macroeconomics (the study of decentralized economies that are less than perfectly coordinated) as follows:

What’s the use of “general competitive equilibrium” if it can’t furnish a sturdy, albeit “external,” foundation for the kind of modeling done by Professor Williamson, et al?  Well, there are lots of other uses, but in the context of this discussion, perhaps the most important insight to be gleaned is this: Every aspect of a real economy that Keynes thought important is missing from Arrow and Debreu’s marvelous construction.  Perhaps this is why Axel Leijonhufvud, in reviewing a state-of-the-art New Keynesian DSGE model here, wrote, “It makes me feel transported into a Wonderland of long ago – to a time before macroeconomics was invented.”

To which I would just add that nearly 70 years ago, Paul Samuelson published his magnificent Foundations of Economic Analysis, a work undoubtedly read and mastered by Williamson. But the central contribution of the Foundations was the distinction between equilibrium conditions and what Samuelson (owing to the influence of the still fashionable philosophical school called logical positivism) mislabeled meaningful theorems. A mere equilibrium condition is not the same as a meaningful theorem, but Samuelson showed how a meaningful theorem can be mathematically derived from an equilibrium condition. The link between equilibrium conditions and meaningful theorems was the foundation of economic analysis. Without a mathematical connection between equilibrium conditions and meaningful theorems analogous to the one provided by Samuelson in the Foundations, claims to have provided microfoundations for macroeconomics are, at best, premature.

The Microfoundations Wars Continue

I see belatedly that the battle over microfoundations continues on the blogosphere, with Paul Krugman, Noah Smith, Adam Posen, and Nick Rowe all challenging the microfoundations position, while Tony Yates and Stephen Williamson defend it with Simon Wren-Lewis trying to serve as a peacemaker of sorts. I agree with most of the criticisms, but what I found most striking was the defense of microfoundations offered by Tony Yates, who expresses the mentality of the microfoundations school so well that I thought that some further commentary on his post would be worthwhile.

Yates’s post was prompted by a Twitter exchange between Yates and Adam Posen after Posen tweeted that microfoundations have no merit, an exaggeration no doubt, but not an unreasonable one. Noah Smith chimed in with a challenge to Yates to defend the proposition that microfoundations do have merit. Hence, the title (“Why Microfoundations Have Merit.”) of Yates’s post. What really caught my attention in Yates’s post is that, in trying to defend the proposition that microfounded models do have merit, Yates offers the following methodological, or perhaps aesthetic, pronouncement .

The merit in any economic thinking or knowledge must lie in it at some point producing an insight, a prediction, a prediction of the consequence of a policy action, that helps someone, or a government, or a society to make their lives better.

Microfounded models are models which tell an explicit story about what the people, firms, and large agents in a model do, and why.  What do they want to achieve, what constraints do they face in going about it?  My own position is that these are the ONLY models that have anything genuinely economic to say about anything.  It’s contestable whether they have any merit or not.

Paraphrasing, I would say that Yates defines merit as a useful insight or prediction into the way the world works. Fair enough. He then defines microfounded models as those models that tell an explicit story about what the agents populating the model are trying to do and the resulting outcomes of their efforts. This strikes me as a definition that includes more than just microfounded models, but let that pass, at least for the moment. Then comes the key point. These models “are the ONLY models that have anything genuinely economic to say about anything.” A breathtaking claim.

In other words, Yates believes that unless an insight, a proposition, or a conjecture, can be logically deduced from microfoundations, it is not economics. So whatever the merits of microfounded models, a non-microfounded model is not, as a matter of principle, an economic model. Talk about methodological authoritarianism.

Having established, to his own satisfaction at any rate, that only microfounded models have a legitimate claim to be considered economic, Yates defends the claim that microfounded models have merit by citing the Lucas critique as an early example of a meritorious insight derived from the “microfoundations project.” Now there is something a bit odd about this claim, because Yates neglects to mention that the Lucas critique, as Lucas himself acknowledged, had been anticipated by earlier economists, including both Keynes and Tinbergen. So if the microfoundations project does indeed have merit, the example chosen to illustrate that merit does nothing to show that the merit is in any way peculiar to the microfoundations project. It is also bears repeating (see my earlier post on the Lucas critique) that the Lucas critique only tells us about steady states, so it provides no useful information, insight, prediction or guidance about using monetary policy to speed up the recovery to a new steady state. So we should be careful not to attribute more merit to the Lucas critique than it actually possesses.

To be sure, in his Twitter exchange with Adam Posen, Yates mentioned several other meritorious contributions from the microfoundations project, each of which Posen rejected because the merit of those contributions lies in the intuition behind the one line idea. To which Yates responded:

This statement is highly perplexing to me.  Economic ideas are claims about what people and firms and governments do, and why, and what unfolds as a consequence.  The models are the ideas.  ‘Intuition’, the verbal counterpart to the models, are not separate things, the origins of the models.  They are utterances to ourselves that arise from us comprehending the logical object of the model, in the same way that our account to ourselves of an equation arises from the model.  One could make an argument for the separateness of ‘intuition’ at best, I think, as classifying it in some cases to be a conjecture about what a possible economic world [a microfounded model] would look like.  Intuition as story-telling to oneself can sometimes be a good check on whether what we have done is nonsense.  But not always.  Lots of results are not immediately intuitive.  That’s not a reason to dismiss it.  (Just like most of modern physics is not intuitive.)  Just a reason to have another think and read through your code carefully.

And Yates’s response is highly perplexing to me. An economic model is usually the product of some thought process intended to construct a coherent model from some mental raw materials (ideas) and resources (knowledge and techniques). The thought process is an attempt to embody some idea or ideas about a posited causal mechanism or about a posited mutual interdependency among variables of interest. The intuition is the idea or insight that some such causal mechanism or mutual interdependency exists. A model is one particular implementation (out of many other possible implementations) of the idea in a way that allows further implications of the idea to be deduced, thereby achieving an enhanced and deeper understanding of the original insight. The “microfoundations project” does not directly determine what kinds of ideas can be modeled, but it does require that models have certain properties to be considered acceptable implementations of any idea. In particular the model must incorporate a dynamic stochastic general equilibrium system with rational expectations and a unique equilibrium. Ideas not tractable given those modeling constraints are excluded. Posen’s point, it seems to me, is not that no worthwhile, meritorious ideas have been modeled within the modeling constraints imposed by the microfoundations project, but that the microfoundations project has done nothing to create or propagate those ideas; it has just forced those ideas to be implemented within the template of the microfoundations project.

None of the characteristic properties of the microfoundations project are assumptions for which there is compelling empirical or theoretical justification. We know how to prove the existence of a general equilibrium for economic models populated by agents satisfying certain rationality assumptions (assumptions for which there is no compelling a priori argument and whose primary justifications are tractability and the accuracy of the empirical implications deduced from them), but the conditions for a unique general equilibrium are way more stringent than the standard convexity assumptions required to prove existence. Moreover, even given the existence of a unique general equilibrium, there is no proof that an economy not in general equilibrium will reach the general equilibrium under the standard rules of price adjustment. Nor is there any empirical evidence to suggest that actual economies are in any sense in a general equilibrium, though one might reasonably suppose that actual economies are from time to time in the neighborhood of a general equilibrium. The rationality of expectations is in one sense an entirely ad hoc assumption, though an inconsistency between the predictions of a model, under the assumption of rational expectations, with the rationally expectations of the agents in the model is surely a sign that there is a problem in the structure of the model. But just because rational expectations can be used to check for latent design flaws in a model, it does not follow that assuming rational expectations leads to empirical implications that are generally, or even occasionally, empirically valid.

Thus, the key assumptions of microfounded models are not logically entailed by any deep axioms; they are imposed by methodological fiat, a philosophically and pragmatically unfounded insistence that certain modeling conventions be adhered to in order to count as “scientific.” Now it would be one thing if these modeling conventions were generating new, previously unknown, empirical relationships or generating more accurate predictions than those generated by non-microfounded models, but evidence that the predictions of microfounded models are better than the predictions of non-microfounded models is notably lacking. Indeed, Carlaw and Lipsey have shown that micro-founded models generate predictions that are less accurate than those generated by non-micofounded models. If microfounded theories represent scientific progress, they ought to be producing an increase, not a decrease, in explanatory power.

The microfoundations project is predicated on a gigantic leap of faith that the existing economy has an underlying structure that corresponds closely enough to the assumptions of the Arrow-Debreu model, suitably adjusted for stochastic elements and a variety of frictions (e.g., Calvo pricing) that may be introduced into the models depending on the modeler’s judgment about what constitutes an allowable friction. This is classic question-begging with a vengeance: arriving at a conclusion by assuming what needs to be proved. Such question begging is not necessarily illegitimate; every research program is based on some degree of faith or optimism that results not yet in hand will justify the effort required to generate those results. What is not legitimate is the claim that ONLY the models based on such question-begging assumptions are genuinely scientific.

This question-begging mentality masquerading as science is actually not unique to the microfoundations school. It is not uncommon among those with an exaggerated belief in the powers of science, a mentality that Hayek called scientism. It is akin to physicalism, the philosophical doctrine that all phenomena are physical. According to physicalism, there are no mental phenomena. What we perceive as mental phenomena, e.g., consciousness, is not real, but an illusion. Our mental states are really nothing but physical states. I do not say that physicalism is false, just that it is a philosophical position, not a proposition derived from science, and certainly not a fact that is, or can be, established by the currently available tools of science. It is a faith that some day — some day probably very, very far off into the future — science will demonstrate that our mental processes can be reduced to, and derived from, the laws of physics. Similarly, given the inability to account for observed fluctuations of output and employment in terms of microfoundations, the assertion that only microfounded models are scientific is simply an expression of faith in some, as yet unknown, future discovery, not a claim supported by any available scientific proof or evidence.


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.

Archives

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

Join 2,282 other followers

Follow Uneasy Money on WordPress.com
Advertisements