Težka tema za poletje, ampak ena izmed ključnih tem za pravilno dojemanje makroekonomije. Za tiste, ki niste sledili dosedanjim postom o tej temi na tem ali ostalih blogih: sredi 1970. let je Robert Lucas razvil teorijo racionalnih pričakovanj, na podlagi katere je prišlo do t.i. makroekonomske revolucije, torej do nastanka t.i. mikrofundiranih makroekonomskih modelov, ki temeljijo na optimizacijskem obnašanju enega samega popolnoma racionalnega reprezentativnega posameznika. In to je osnova za dinamične stohastične modele splošnega ravnotežja (DSGE), ki jih uporabljajo centralne banke za napovedi makro agregatov. To modeli so seveda grdo udarili mimo pri napovedih v času velikih eksogenih šokov, kot je bila sedanja kriza.
Spodaj je izsek iz intervjuja z nobelovcem Jamesom Heckmanom, prav tako iz Chicago University, ki pravi, da sta tako on kot Milton Friedman opozarjala, da so nekateri teorijo racionalnih pričakovanj vzeli preveč resno, kar je privedlo do velikega razkoraka med teorijo in dejstvi (podatki). Povzeto po ekonomskem zgodovinarju Larsu P. Syllu:
James Heckman, winner of the “Nobel Prize” in economics (2000), did an interview with John Cassidy in 2010. It’s an interesting read (Cassidy’s words in italics):
What about the rational-expectations hypothesis, the other big theory associated with modern Chicago? How does that stack up now?
I could tell you a story about my friend and colleague Milton Friedman. In the nineteen-seventies, we were sitting in the Ph.D. oral examination of a Chicago economist who has gone on to make his mark in the world. His thesis was on rational expectations. After he’d left, Friedman turned to me and said, “Look, I think it is a good idea, but these guys have taken it way too far.”
It became a kind of tautology that had enormously powerful policy implications, in theory. But the fact is, it didn’t have any empirical content. When Tom Sargent, Lard Hansen, and others tried to test it using cross equation restrictions, and so on, the data rejected the theories. There were a certain section of people that really got carried away. It became quite stifling.
What about Robert Lucas? He came up with a lot of these theories. Does he bear responsibility?
Well, Lucas is a very subtle person, and he is mainly concerned with theory. He doesn’t make a lot of empirical statements. I don’t think Bob got carried away, but some of his disciples did. It often happens. The further down the food chain you go, the more the zealots take over.
What about you? When rational expectations was sweeping economics, what was your reaction to it? I know you are primarily a micro guy, but what did you think?
What struck me was that we knew Keynesian theory was still alive in the banks and on Wall Street. Economists in those areas relied on Keynesian models to make short-run forecasts. It seemed strange to me that they would continue to do this if it had been theoretically proven that these models didn’t work.
What about the efficient-markets hypothesis? Did Chicago economists go too far in promoting that theory, too?
Some did. But there is a lot of diversity here. You can go office to office and get a different view.
[Heckman brought up the memoir of the late Fischer Black, one of the founders of the Black-Scholes option-pricing model, in which he says that financial markets tend to wander around, and don’t stick closely to economics fundamentals.]
[Black] was very close to the markets, and he had a feel for them, and he was very skeptical. And he was a Chicago economist. But there was an element of dogma in support of the efficient-market hypothesis. People like Raghu [Rajan] and Ned Gramlich [a former governor of the Federal Reserve, who died in 2007] were warning something was wrong, and they were ignored. There was sort of a culture of efficient markets—on Wall Street, in Washington, and in parts of academia, including Chicago.
What was the reaction here when the crisis struck?
Everybody was blindsided by the magnitude of what happened. But it wasn’t just here. The whole profession was blindsided. I don’t think Joe Stiglitz was forecasting a collapse in the mortgage market and large-scale banking collapses.
So, today, what survives of the Chicago School? What is left?
I think the tradition of incorporating theory into your economic thinking and confronting it with data—that is still very much alive. It might be in the study of wage inequality, or labor supply responses to taxes, or whatever. And the idea that people respond rationally to incentives is also still central. Nothing has invalidated that—on the contrary.
So, I think the underlying ideas of the Chicago School are still very powerful. The basis of the rocket is still intact. It is what I see as the booster stage—the rational-expectation hypothesis and the vulgar versions of the efficient-markets hypothesis that have run into trouble. They have taken a beating—no doubt about that. I think that what happened is that people got too far away from the data, and confronting ideas with data. That part of the Chicago tradition was neglected, and it was a strong part of the tradition.
When Bob Lucas was writing that the Great Depression was people taking extended vacations—refusing to take available jobs at low wages—there was another Chicago economist, Albert Rees, who was writing in the Chicago Journal saying, No, wait a minute. There is a lot of evidence that this is not true.
Milton Friedman—he was a macro theorist, but he was less driven by theory and by the desire to construct a single overarching theory than by attempting to answer empirical questions. Again, if you read his empirical books they are full of empirical data. That side of his legacy was neglected, I think.
When Friedman died, a couple of years ago, we had a symposium for the alumni devoted to the Friedman legacy. I was talking about the permanent income hypothesis; Lucas was talking about rational expectations. We have some bright alums. One woman got up and said, “Look at the evidence on 401k plans and how people misuse them, or don’t use them. Are you really saying that people look ahead and plan ahead rationally?” And Lucas said, “Yes, that’s what the theory of rational expectations says, and that’s part of Friedman’s legacy.” I said, “No, it isn’t. He was much more empirically minded than that.” People took one part of his legacy and forgot the rest. They moved too far away from the data.
Yes indeed, they certainly “moved too far away from the data.”
In one of the more well-known and highly respected evaluation reviews made, Michael Lovell (1986) concluded:
it seems to me that the weight of empirical evidence is sufficiently strong to compel us to suspend belief in the hypothesis of rational expectations, pending the accumulation of additional empirical evidence.
And this is how Nikolay Gertchev summarizes studies on the empirical correctness of the hypothesis:
More recently, it even has been argued that the very conclusions of dynamic models assuming rational expectations are contrary to reality: “the dynamic implications of many of the specifications that assume rational expectations and optimizing behavior are often seriously at odds with the data” (Estrella and Fuhrer 2002, p. 1013). It is hence clear that if taken as an empirical behavioral assumption, the RE hypothesis is plainly false; if considered only as a theoretical tool, it is unfounded and selfcontradictory.