Thursday, October 20, 2016

Klingian Philosophy of Economic Science

by Levi Russell

One of my favorite things to do in this blog is to talk about unconventional perspectives on economic theory. A great source for such unconventional views is Arnold Kling's blog. The recent Nobel Prize awarded to Oliver Hart and Bengt Holmstrom prompted Kling to write a series of posts detailing his views on economic theory, specifically about the epistemology of economics. Kling's own brand of unconventionality is especially interesting given that he received his PhD from MIT. Below I reproduce a post from last week:

A commenter writes,
So in your opinion intuition is sufficient. As long as we can tell an intuitive story about something, that is as good as proving it?
I think that “proof” is too high a standard to use in economics. If our knowledge is limited to what we can prove, then we do not know anything. I think that we have frameworks of interpretation which give us insights. This is knowledge, even if it is not as definitive or reliable as knowledge in physics or chemistry.

As an example, take factor-price equalization. The insight is that the easier it is to trade across countries, the more that factor prices will tend to converge. I think that this is an important insight. It is one of what I call the Four Forces driving social and economic trends in recent decades. (The other three are assortative mating, the shift away from manufacturing toward health care and education, and the Internet.)

Paul Samuelson proved a “factor-price equalization theorem” for a special case of two factors, two goods and two countries. However, it is very difficult, if not impossible, to extend that theorem to make it realistic, including the fact that not all industries are subject to diminishing returns. In my view, Samuelson’s theorem per se offers no insight, because it is so narrow in scope. The unprovable broader insight is what is useful.

Incidentally, I also think that factor-price equalization is hard to prove statistically. Too many other things are happening at once to be able to say definitively that factor-price equalization is having an effect, say, on unskilled workers’ wages in the U.S. and China. I believe that it is having an effect, and there are studies that support my view, but it is not provable.

In order to prove something mathematically, you have to make narrow assumptions. In physics or engineering, this often works out well. When you roll a ball down an inclined plane, ignoring friction causes only a small error in the calculation.

In economics, the factors that you leave out in order to build a mathematical model tend to be more important. As a result, the requirement to express ideas in the form of mathematical models is harmful in two ways. We waste time proving false theorems and we miss out on useful insights.
The narrow assumptions lead you to prove something which is false in the real world.. For example, the central insight of the “market for lemons” proof is that a used car market cannot work. However, once we expand the assumptions to allow for warranties, dealer reputations, mechanics’ inspections, and so on, the original theorem does not hold.

Meanwhile, there are insights that are missed because they cannot be represented in an elegant mathematical way. A lot of the insights that I offer in Specialization and Trade fall in that category.
Our goal should be to acquire knowledge. The demand for proof hurts rather than helps with that process.
Bonus: I really enjoyed this piece from the Sloan Management Review published back in 2011.

Teaser: I'll be giving my thoughts on the Baysanto merger later this week or weekend.

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