Archive for the 'Paul Romer' Category

Paul Romer on Modern Macroeconomics, Or, the “All Models Are False” Dodge

Paul Romer has been engaged for some time in a worthy campaign against the travesty of modern macroeconomics. A little over a year ago I commented favorably about Romer’s takedown of Robert Lucas, but I also defended George Stigler against what I thought was an unfair attempt by Romer to identify George Stigler as an inspiration and role model for Lucas’s transgressions. Now just a week ago, a paper based on Romer’s Commons Memorial Lecture to the Omicron Delta Epsilon Society, has become just about the hottest item in the econ-blogosophere, even drawing the attention of Daniel Drezner in the Washington Post.

I have already written critically about modern macroeconomics in my five years of blogging, and here are some links to previous posts (link, link, link, link). It’s good to see that Romer is continuing to voice his criticisms, and that they are gaining a lot of attention. But the macroeconomic hierarchy is used to criticism, and has its standard responses to criticism, which are being dutifully deployed by defenders of the powers that be.

Romer’s most effective rhetorical strategy is to point out that the RBC core of modern DSGE models posit unobservable taste and technology shocks to account for fluctuations in the economic time series, but that these taste and technology shocks are themselves simply inferred from the fluctuations in the times-series data, so that the entire structure of modern macroeconometrics is little more than an elaborate and sophisticated exercise in question-begging.

In this post, I just want to highlight one of the favorite catch-phrases of modern macroeconomics which serves as a kind of default excuse and self-justification for the rampant empirical failures of modern macroeconomics (documented by Lipsey and Carlaw as I showed in this post). When confronted by evidence that the predictions of their models are wrong, the standard and almost comically self-confident response of the modern macroeconomists is: All models are false. By which the modern macroeconomists apparently mean something like: “And if they are all false anyway, you can’t hold us accountable, because any model can be proven wrong. What really matters is that our models, being microfounded, are not subject to the Lucas Critique, and since all other models than ours are not micro-founded, and, therefore, being subject to the Lucas Critique, they are simply unworthy of consideration. This is what I have called methodological arrogance. That response is simply not true, because the Lucas Critique applies even to micro-founded models, those models being strictly valid only in equilibrium settings and being unable to predict the adjustment of economies in the transition between equilibrium states. All models are subject to the Lucas Critique.

Here is Romer’s take:

In response to the observation that the shocks are imaginary, a standard defense invokes Milton Friedman’s (1953) methodological assertion from unnamed authority that “the more significant the theory, the more unrealistic the assumptions (p.14).” More recently, “all models are false” seems to have become the universal hand-wave for dismissing any fact that does not conform to the model that is the current favorite.

Friedman’s methodological assertion would have been correct had Friedman substituted “simple” for “unrealistic.” Sometimes simplifications are unrealistic, but they don’t have to be. A simplification is a generalization of something complicated. By simplifying, we can transform a problem that had been too complex to handle into a problem more easily analyzed. But such simplifications aren’t necessarily unrealistic. To say that all models are false is simply a dodge to avoid having to account for failure. The excuse of course is that all those other models are subject to the Lucas Critique, so my model wins. But your model is subject to the Lucas Critique even though you claim it’s not, so even according to the rules you have arbitrarily laid down, you don’t win.

So I was just curious about where the little phrase “all models are false” came from. I was expecting that Karl Popper might have said it, in which case to use the phrase as a defense mechanism against empirical refutation would have been a particularly fraudulent tactic, because it would have been a perversion of Popper’s methodological stance, which was to force our theoretical constructs to face up to, not to insulate it from, empirical testing. But when I googled “all theories are false” what I found was not Popper, but the British statistician, G. E. P. Box who wrote in his paper “Science and Statistics” based on his R. A. Fisher Memorial Lecture to the American Statistical Association: “All models are wrong.” Here’s the exact quote:

Since all models are wrong the scientist cannot obtain a “correct” one by excessive elaboration. On the contrary following William of Occam he should seek an economical description of natural phenomena. Just as the ability to devise simple but evocative models is the signature of the great scientist so overelaboration and overparameterization is often the mark of mediocrity.

Since all models are wrong the scientist must be alert to what is importantly wrong. It is inappropriate to be concerned about mice when there are tigers abroad. Pure mathematics is concerned with propositions like “given that A is true, does B necessarily follow?” Since the statement is a conditional one, it has nothing whatsoever to do with the truth of A nor of the consequences B in relation to real life. The pure mathematician, acting in that capacity, need not, and perhaps should not, have any contact with practical matters at all.

In applying mathematics to subjects such as physics or statistics we make tentative assumptions about the real world which we know are false but which we believe may be useful nonetheless. The physicist knows that particles have mass and yet certain results, approximating what really happens, may be derived from the assumption that they do not. Equally, the statistician knows, for example, that in nature there never was a normal distribution, there never was a straight line, yet with normal and linear assumptions, known to be false, he can often derive results which match, to a useful approximation, those found in the real world. It follows that, although rigorous derivation of logical consequences is of great importance to statistics, such derivations are necessarily encapsulated in the knowledge that premise, and hence consequence, do not describe natural truth.

It follows that we cannot know that any statistical technique we develop is useful unless we use it. Major advances in science and in the science of statistics in particular, usually occur, therefore, as the result of the theory-practice iteration.

One of the most annoying conceits of modern macroeconomists is the constant self-congratulatory references to themselves as scientists because of their ostentatious use of axiomatic reasoning, formal proofs, and higher mathematical techniques. The tiresome self-congratulation might get toned down ever so slightly if they bothered to read and take to heart Box’s lecture.

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In Defense of Stigler

I recently discussed Paul Romer’s criticism of Robert Lucas for shifting from the Feynman integrity that, in Romer’s view, characterized Lucas’s early work, to the Stigler conviction that Romer believes has characterized Lucas’s later work. I wanted to make a criticism of Lucas different from Romer’s, so I only suggested in passing that that the Stigler conviction criticized by Romer didn’t seem that terrible to me, and I compared Stigler conviction to Galileo’s defense of Copernican heliocentrism. Now, having reread the essay, “The Nature and Role of Originality in Scientific Progress,” from which Romer quoted, I find, as I suspected, that Romer has inaccurately conveyed the message that Stigler meant to convey in his essay.

In accusing Lucas of forsaking the path of Feynman integrity and chosing instead the path of Stigler conviction, making it seem as if Stigler had provided justification for pursuing an ideological agenda, as Romer believes Lucas and other freshwater economists have done, Romer provides no information about the context of Stigler’s essay. Much of Stigler’s early writing in economics was about the history of economics, and Stigler’s paper on originality is one of those; in fact, it was subsequently republished as the lead essay in Stigler’s 1965 volume Essays in the History of Economics. What concerns Stigler in the essay are a few closely related questions: 1) what characteristic of originality makes it highly valued in science in general and in economics in particular? 2) Given that originality is so highly valued, how do economists earn a reputation for originality? 3) Is the quest for originality actually conducive to scientific progress?

Here is Stigler’s answer to the first question provided at the end of the introductory section under the heading “The Meaning of Originality.”

Scientific originality in its important role should be measured against the knowledge of a man’s contemporaries. If he opens their eyes to new ideas or to new perspectives on old ideas, he is an original economist in the scientifically important sense. . . . Smith, Ricardo, Jevons, Walras, Marshall, Keynes – they all changed the beliefs of economists and thus changed economics.

It is conceivable for an economist to be ignored by contemporaries and yet exert considerable influence on later generations, but this is a most improbable event. He must have been extraordinarily out of tune with (in advance of?) his times, and rarely do first-class minds throw themselves away on the visionary. Perhaps Cournot is an example of a man whose work skipped a half a century, but normally such men become famous only by reflecting the later fame of the rediscovered doctrines.

Originality then in its scientifically important role, is a matter of subtle unaccustomedness – neither excessive radicalism nor statement of the previous unformulated consensus.

The extended passage quoted by Romer appears a few paragraphs later in the second section of the paper under the heading “The Techniques of Persuasion.” Having already established that scientific originality must be both somehow surprising yet also capable of being understood by other economists, Stigler wants to know how an original economist can get the attention of his peers for his new idea. Doing so is not easy, because

New ideas are even harder to sell than new products. Inertia and the many unharmonious voices of those who would change our ways combine against the balanced and temperate statement of the merits of one’s ” original ” views. One must put on the best face possible, and much is possible. Wares must be shouted — the human mind is not a divining rod that quivers over truth.

It is this analogy between the selling of new ideas and selling of new products that leads Stigler in his drollery to suggest that with two highly unusual exceptions – Smith and Marshall – all economists have had to resort to “the techniques of the huckster.”

What are those techniques? And who used them? Although Stigler asserted that all but two famous economists used such techniques, he mentioned only two by name, and helpfully provided the specific evidence of their resort to huckster-like self-promotional techniques. Whom did Stigler single out for attention? William Stanley Jevons and Eugen von Bohm-Bawerk.

So what was the hucksterism committed by Jevons? Get ready to be shocked:

Writing a Theory of Political Economy, he devoted the first 197 pages of a book of 267 pages to his ideas on utility!

OMG! Shocking; just shocking. How could he have stooped so low as that? But Bohm-Bawerk was even worse.

Not content with writing two volumes, and dozens of articles, in presenting and defending his capital theory, he added a third volume (to the third edition of his Positive Theorie des Kapitals) devoted exclusively to refuting, at least to his own satisfaction, every criticism that had arisen during the preceding decades.

What a sordid character that loathsome Austrian aristocrat must have been! Publishing a third volume devoted entirely to responding to criticisms of the first two. The idea!

Well, actually, they weren’t as bad as you might have thought. Let’s read Stigler’s next paragraph.

Although the new economic theories are introduced by the technique of the huckster, I should add that they are not the work of mere hucksters. The sincerity of Jevons, for example, is printed on every page. Indeed I do not believe that any important economist has ever deliberately contrived ideas in which he did not believe in order to achieve prominence: men of the requisite intellectual power and morality can get bigger prizes elsewhere. Instead, the successful inventor is a one-sided man. He is utterly persuaded of the significance and correctness of his ideas and he subordinates all other truths because they seem to him less important than the general acceptance of his truth. He is more a warrior against ignorance than a scholar among ideas.

I believe that Romer misunderstood what Stigler mean to say here. Romer seems to interpret this passage to mean that if a theorist is utterly convinced that he is right, he somehow can be justified in “subordinat[ing] all other truths” in cutting corners, avoiding contrary arguments or suppressing contradictory evidence that might undercut his theory – the sorts of practices ruled out by Feynman integrity, which is precisely what Romer was accusing Lucas of having done in a paper on growth theory. But to me it is clear from the context that what Stigler meant by “subordinating all other truths” was not any lack of Feynman integrity, but the single-minded focus on a specific contribution to the exclusion of all others. That was why Stigler drew attention to the exorbitant share of Jevons’s book entitled Principles of Political Economy devoted to the theory of marginal utility or the publication by Bohm-Bawerk of an entire volume devoted to responding to criticisms of his two earlier volumes on the theory of capital and interest. He neither implied nor meant to suggest that either Jevons or Bohm-Bawerk committed any breach of scientific propriety, much less Feynman integrity.

If there were any doubt about the correctness of this interpretation of what Stigler meant, it would be dispelled by the third section of Stigler’s paper under the heading: “The Case of Mill.”

John Stuart Mill is a striking example with which to illustrate the foregoing remarks. He is now considered a mediocre economist of unusual literary power; a fluent, flabby echo of Ricardo. This judgement is well-nigh universal: I do not believe that Mill has had a fervent admirer in the twentieth century. I attribute this low reputation to the fact that Mill had the perspective and balance, but not the full powers, of Smith and Marshall. He avoided all the tactics of easy success. He wrote with extraordinary balance, and his own ideas-considering their importance-received unbelievably little emphasis. The bland prose moved sedately over a corpus of knowledge organized with due regard to structure and significance, and hardly at all with regard to parentage. . . .

Yet however one judges Mill, it cannot be denied that he was original. In terms of identifiable theories, he was one of the most original economists in the history of the science.

Stigler went on to list and document the following original contributions of Mill in the area of value theory, ignoring Mill’s contributions to trade theory, “because I cannot be confident of the priorities.”

1 Non-competing Groups

2 Joint Products

3 Alternative Costs

4 The Economics of the Firm

5 Supply and Demand

6 Say’s Law

Stigler concludes his discussion with this assessment of Mill

This is a very respectable list of contributions. But it is also a peculiar list: any one of the contributions could be made independently of all the others. Mill was not trying to build a new system but only to add improvements here and there to the Ricardian system. The fairest of economists, as Schumpeter has properly characterized Mill, unselfishly dedicated his abilities to the advancement of the science. And, yet, Mill’s magisterial quality and conciliatory tone may have served less well than sharp and opinionated controversy in inciting his contemporaries to make advances.

Finally, just to confirm the lack of ideological motivation in Stigler’s discussion, let me quote Stigler’s characteristically ironic and playful conclusion.

These reflections on the nature and role of originality, however, have no utilitarian purpose, or even a propagandistic purpose. If I have a prejudice, it is that we commonly exaggerate the merits of originality in economics–that we are unjust in conferring immortality upon the authors of absurd theories while we forget the fine, if not particularly original, work of others. But I do not propose that we do something about it.


About Me

David Glasner
Washington, DC

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

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