Rational expectations – a panel discussion with Robert Lucas

27 Dec, 2014 at 19:24 | Posted in Economics | 1 Comment

S1365100513000345a_abstract Kevin Hoover: Let me follow up on my question to make it more pointed so that Mike Lovell and others can comment on it. In 1986, Mike, you wrote a pretty well known paper in which you examined the empirical success of a variety of alternatives to rational expectations, including adaptive expectations, structural expectations, and implicit expectations [Lovell (1986)]. And in your paper, rational expectations does not dominate these alternatives. You even cite a paper by Muth, which comes down more or less in favor of implicit expectations. What I am wondering, then, is that, given the way that you have approached this empirically or the way it could be approached empirically, does this mean that we should find an alternative to rational expectations or are there other expectational approaches that are an empirical complement to rational expectations?

Michael Lovell: I wish Jack Muth could be here to answer that question, but obviously he can’t because he died just as Hurricane Wilma was zeroing in on his home on the Florida Keys. But he did send me a letter in 1984. This was a letter in response to an earlier draft of that paper you are referring to. I sent Jack my paper with some trepidation because it was not encouraging to his theory. And much to my surprise, he wrote back. This was in October 1984. And he said: “I came up with some conclusions similar to some of yours on the basis of forecasts of business activity compiled by the Bureau of Business Research at Pitt.” [Letter Muth to Lovell (2 October 1984)] He had got hold of the data from five business firms, including expectations data, analyzed it, and found that the rational expectations model did not pass the empirical test. He went on to say, “It is a little surprising that serious alternatives to rational expectations have never really been proposed. My original paper was largely a reaction against very naıve expectations hypotheses juxtaposed with highly rational decision-making behavior and seems to have been rather widely misinterpreted. Two directions seem to be worth exploring: (1) explaining why smoothing rules work and their limitations and (2) incorporating well known cognitive biases into expectations theory (Kahneman and Tversky). It was really incredible that so little has been done along these lines.” Muth also said that his results showed that expectations were not in accordance with the facts about forecasts of demand and production. He then advanced an alternative to rational expectations. That alternative he called an “errors-in-the- variables” model. That is to say, it allowed the expectation error to be correlated with both the realization and the prediction. Muth found that his errors-in-variables model worked better than rational expectations or Mills’ implicit expectations, but it did not entirely pass the tests. In a shortened version of his paper published in the Eastern Economic Journal he reported: “The results of the analysis do not support the hypotheses of the naive, exponential, extrapolative, regressive, or rational models. Only the expectations revision model used by Meiselman is consistently supported by the statistical results. . . . These conclusions should be regarded as highly tentative and only suggestive, however, because of the small number of firms studied.” [Muth (1985, p. 200)] Muth thought that we should not only have rational expectations, but if we’re going to have rational behavioral equations, then consistency requires that our model include rational expectations. But he was also interested in the results of people who do behavioral economics, which at that time was a very undeveloped area.

Hoover: Does anyone else want to comment on issue of testing rational expec-tations against alternatives and if it matters whether rational expectations stands up to empirical tests or whether it is not the sort of thing for which testing would be relevant?

Robert Shiller: What comes to my mind is that rational expectations models have to assume away the problem of regime change, and that makes them hard to apply. It’s the same criticism they make of Kahnemann and Tversky, that the model isn’t clear and crisp about exactly how you should apply it. Well, the same is true for rational expectations models. And there’s a new strand of thought that’s getting impetus lately, that the failure to predict this crisis was a failure to understand regime changes … Omitting key variables because we don’t have the data history on them creates a fundamental problem That’s why many nice concepts don’t find their way into empirical models and are not used more. They remain just a conceptual model …

Hoover: Bob, did you want to comment on that? You’re looking unhappy, I thought.

Robert Lucas: No. I mean, you can’t read Muth’s paper as some recipe for cranking out true theories about everything under the sun—we don’t have a recipe like that. My paper on expectations and the neutrality of money was an attempt to get a positive theory about what observations we call a Phillips curve. Basically it didn’t work. After several years, trying to push that model in a direction of being more operational, it didn’t seem to explain it. So we had what we call price stickiness, which seems to be central to the way the system works. I thought my model was going to explain price stickiness, and it didn’t. So we’re still working on it; somebody’s working on it. I don’t think we have a satisfactory solution to that problem, but I don’t think that’s a cloud over Muth’s work. If Jack thinks it is, I don’t agree with him. Mike cites some data that Jack couldn’t make sense out of using rational expectations. . . . There’re a lot of bad models out there. I authored my share, and I don’t see how that affects a lot of things we’ve been talking about earlier on about the value of Muth’s contribution.

Warren Young: Just to wrap up the issue of possible alternatives to rational expectations or complements to rational expectations. Does behavioral economics or psychology in general provide a useful and viable alternative to rational expectations, with the emphasis on “useful”? {laughter}

Shiller: Well, that’s the criticism of behavioral economics, that it doesn’t provide elegant models. If you read Kahnemann and Tversky, they say that preferences have a kink in them, and that kink moves around depending on framing. But framing is hard to pin down. So we don’t have any elegant behavioral economics models. The job isn’t done, and economists have to read widely and think about these issues. I am sorry, I don’t have a good answer. My opinion is that behavioral economics has to be on the reading list. Ultimately, the whole rationality assumption is another thing; it’s interesting to look back on the history of it. Back at the turn of the century—around 1900—when utility-maximizing economic theory was being discovered, it was described as a psychological theory—did you know that, that utility maximization was a psychological theory? … The idea about rational expectations, again, reflects insights about people—that if you show people recurring patterns in the data, they can actually process it—a little bit like an ARIMA model—and they can start using some kind of brain faculties that we do not fully comprehend. They can forecast— it’s an intuitive thing that evolved and it’s in our psychology. So, I don’t think that there’s a conflict between behavioral economics and classical economics. It’s all something that will evolve responding to each other—psychology and economics.

Lucas: I totally disagree.

Hoover: The Great Recession and the recent financial crisis have been widely viewed in both popular and professional commentary as a challenge to rational expectations and to efficient markets. I really just want to get your comments on that strain of the popular debate that’s been active over the last couple years …

Lucas: You know, people had no trouble having financial meltdowns in their economies before all this stuff we’ve been talking about came on board. We didn’t help, though; there’s no question about that. We may have focused attention on the wrong things; I don’t know.

Shiller: Well, I’ve written several books on that. … Another name that’s not been mentioned is John Maynard Keynes. I suspect that he’s not popular with everyone on this panel … To understand Keynes, you have to go back to his 1921 book, Treatise on Probability … He said—he’s really into almost this regime-change thing that we brought up before—that people don’t have probabilities, except in very narrow, special circumstances. You can think of a coin-toss experiment, and then you know what the probabilities are. But in macroeconomics, it’s always fuzzy.

1 Comment

  1. Quite informative discussion. In my view, it shows how the “imperialism” of rational exception is a “tab” overstated! Very early on, its limitations were recognized.


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