Yale Q6 Fall 2009 Q&A with Dr. Shiller

Decades of economic research have assumed people pursue their goals in a rational manner, discounting the effects of emotion, bias, error, and other irrational forces. Robert Shiller argues that economists need to take a closer look at how people make decisions.

Q: How important is it to understand what people are thinking and feeling when you are trying to understand the economy as a whole?

That's been a controversial question in economics for a long time. Milton Friedman wrote a collection of essays in 1953 called Essays in Positive Economics, in which he argued that you shouldn't try to infer what people are thinking because people really can't tell you what they're thinking. If you ask people why they did something, they will give you a conventional answer or mislead you. The idea was that the essence of economics is to look at the constraints that people have and assume that people are behaving rationally, subject to those constraints, and interpret economic data as reflecting that rational behavior. That is the defining characteristic of economics as a discipline — as opposed to psychology as a discipline — that, in understanding something as massive as the economy, it's best to look at people's actions, not their ostensible reasons. There is some appeal to that. I just wish it were more right.

I can get enthusiastic talking about this theory because, in some respects, it is good. To give an example, suppose you are trying to understand the seasonality of food prices — why they go up in the winter and down in the summer. Well, it's pretty obvious that it has something to do with the weather as a constraint, but you better think it through, because we live in a global economy, and when it's winter up here, it's summer down south. Obviously they'll ship food from one hemisphere to another. That puts a limit on seasonality. This is pure economics, and I'm sure it's right, because the seasons occur year after year after year, and you have people whose job is to ship fruits and vegetables and food around. They're going to find the best pattern of shipping, given all the costs. It wouldn't make a lot of sense to ignore that. Thinking that people get emotional in the summer, or something like that, would probably be wrong.

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