Beating the dead horse of rational expectations...

The above award should be given to University of Oxford economist Simon Wren-Lewis for concocting yet another defense of the indefensible idea of Rational Expectations (RE). Gotta admire his determination. I've written about this idea many times (here and here, for example), and I thought it had died a death, but that was obviously not true. I'm not going to say too much except to note that the strategy of the Wren-Lewis argument is essentially to ask "what are the alternatives to Rational Expectations?," then to mention just one possible alternative that he calls "naive adaptive expectations," and then to go on to criticize this silly alternative as being unrealistic, which it indeed is. But that's no defense of RE.

He doesn't ever address the question of why economists don't use more realistic ways to model how people form their expectations, for example by looking to psychology and experimental studies of how people learn (especially through social interactions and copying behavior). The only defense he offers on that score is to say they don't want too many details because they seek a "simple" way to model expectations so they can solve their favorite macroeconomic models. That fact that this renders such models possibly quite useless and misleading as guides to the real world doesn't seem to give him (or others) pause.

Lars Syll was a target in the Wren-Lewis post and has a nice rejoinder here. In comments, others raised concerns about why Lars didn't mentioned specific alternatives to RE. I added a comment there, which I'll reproduce here:

It seems to me that there are clear alternatives to rational expectations and I'm not sure why economists seem loath to use then. Simon Wren-Lewis gives one alternative as naive "adaptive expectations", but this seems like a straw man. Here people seem to believe more or less that trends will continue. That is truly naive. Expectations are important and the psychological literature on learning suggests that people form them in many ways, with heuristic theories and rules of thumb, and then adjust their use of these heuristics through experience. This is the kind of adaptive expectations that ought to be used in macro models.

From what I have read, however, the vast "learning literature" in macroeconomics that defenders of RE often refer to really doesn't go very far in exploring learning. A review I read as recently as 2009 used learning algorithms which ASSUMED that people already know the right model of the economy and only need to learn the values of some parameters. I suspect this is done on purpose so that the learning process converges to RE -- and an apparent defense of RE is therefore achieved. But this is only a trick. Use more realistic learning behavior to model expectations and you find little convergence at all -- just ongoing learning as the economy itself keeps doing new things in ways the participants never quite manage to predict.

As Simon Wren-Lewis himself notes, " it is worth noting that a key organising device for much of the learning literature is the extent to which learning converges towards rational expectations." So again, it seems as if the purpose of the model is to see how we can get the conclusion we want, not to explore the kinds of things we might actually expect to see in the world. This is what makes people angry and I think rightfully about the RE idea. I suspect that REAL reason for this is that, if one uses more plausible learning behavior (not the silly naive kind of adaptive expectations), you find that your economy isn't guaranteed to settle down to any kind of equilibrium, and you can't say anything honestly about the welfare of any outcomes, and so most of what has been developed in economics turns out to be pretty useless. Most economists find that too much to stomach.

One day soon I hope this subject really will be a dead horse.

Rational -- by definition and ideology

I've been doing some background reading on rationality in economics, and came across this fairly unique perspective offered by economist Duncan Foley. It's from 2003. What sets it apart from most other reviews of the role of the rationality assumption in economics, is that Foley tries to trace the history of this approach as it emerged out of the tradition of Hobbes and Locke in political philosophy. As Foley notes, the idea of rationality is in many ways beyond question for most economists, and not at all an empirical matter:

...an orientation toward situating explanations of economic phenomena in relation to rationality has increasingly become the touchstone by which mainstream economists identify themselves and recognize each other. This is not so much a question of adherence to any particular conception of rationality, but of taking rationality of individual behavior as the unquestioned starting point of economic analysis.

 It has become so, he asserts, because this way of thinking has emerged from the "just so" story developed by Hobbes, Locke and others which allegedly explains how property rights and political institutions solve problems arising from the anarchic struggle of man against man in the original state of nature. They place reason at the core of this project, and essentially use this story to explain why things are as they are -- this is the rational world and the only way things can be, if we are to avoid the chaos of anarchy. In essence, the rationality assumption is part of a propaganda campaign. Foley:

A hallmark of these [rationally designed] institutions is that they are in themselves in principle democratic and egalitarian (everyone has an equal right to vote or to hold property) but lead
inexorably to sharp inequalities in economic well-being. It is not hard to see that an economic science whose philosophical starting point was not rational individual action would create an embarrassing discord with this political tradition. The whole point of the Hobbes-Locke “discourse” (to use the jargon of post-modernism) is to rationalize the existing inequalities of power and economic well-being that arise from the institutions of modern society as being unavoidable consequences of the interaction of naturally constituted rational individuals
confronting each other as equals, given the natural and unalterable conditions of human existence. Economic science has a place in this grand project only insofar as it can relate itself to the same philosophical foundations.

I think there's a strong current of truth here. There is in today's economic theory a standing presumption that people should be modelled as rational decision makers (optimizers), and the argument often seems to boil down (in some disguised form) to "we must, because if we do not, we will not be able to prove theorems about equilibrium and its efficiency." This is of course too strong, and research programs in behavioural economics, information asymmetries and so on seem to be working to correct this, but the effort required reflects how much resistance there is to such change and how much intellectual inertia still resides in the idea of thorough-going rationality. Foley suggests that efforts to bring more realistic perspectives such as bounded rationality into core theory have been resisted precisely because they cannot be used to justify the just-so story of the efficient equilibrium:

...in its pragmatic focus on understanding and explaining how people actually behave in modern society, bounded rationality loses contact with the underlying project of rationalizing the institutions of modern society. For example, there really is no logical place in the discourse of bounded rationality for the Fundamental Theorems of Welfare Economics that purport to establish a connection between competitive market equilibrium and an efficient allocation of resources.

 I think he may largely be right. If so, this would go a long way to explaining why economics has persisted with such a narrow set of theoretical concepts for such a long time. Maybe it's not actually trying to explain and understand the world at all, but to rationalize why it is OK that it is as we see it. And that's not encouraging for those of us hoping it will change in a big way:

It will not be easy to create a social science that transcends the antinomies and limitations of rational-actor theory. Certainly we cannot depend on the “usual” processes of scientific self-criticism to accomplish much in this direction. No accumulation of its empirical anomalies, or demonstration of its logical inadequacies will somehow magically dispel the power of rational-actor theory, because its power does not rest in the last instance on the adequacy of its
explanations or the consistency of its logic.

Economists on the way to being a "religious cult"...

A short seven minute video produced by the Institute for New Economic Thinking offers the views (very briefly) of a number of economists on modeling and it's purposes (h/t to Moneyscience). Two things of note:

1. Along the way, Brad DeLong mentions Milton Friedman's famous claim that a model is better the more unrealistic its assumptions, and that the sole measure of a theory is making accurate predictions. I'd really like to know what DeLong thinks on this, but his views aren't there in the interview. He mentions Friedman's idea but doesn't defend or attack it, just a reference to one of the most influential ideas on this topic, I guess. Shows how much Friedman's view is still in play.

In my view (some not very well organized thoughts here) the core problem with Friedman's argument is that a theory with perfect predictions and perfectly unrealistic assumptions simply doesn't teach you anything -- you're left just as mystified by how the model can possibly work (give the right predictions) as you were with the original phenomena you set out to explain. It's like a miracle. Such a model might of course be valuable as a starting point, and in stimulating the invention of further models with more realistic assumptions which then -- if they give the same predictions -- may indeed teach you something about how certain kinds of interactions, behaviours, etc (in the assumptions) can lead to observed consequences.

But then -- it's the models with the more realistic assumptions that are superior. (It's worth remembering that Friedman liked to say provocative things even if he didn't quite believe them.)

2. An interesting quote from economist James Galbraith, with which I couldn't agree more:

Modeling is not the end-all and the be-all of economics... The notion that the qualities of an economist should be defined by the modeling style that they adopt [is a disaster]. There is a group of people who say that if you're not doing dynamic stochastic general equilibrium modeling then you're not really a modern economist... that's a preposterous position which is going to lead to the reduction of economics to the equivalent of a small religious cult working on issues of interest to no one else in the world.