What’s Wrong with Economic Theory as Presented to the Public ?

Robert Waldmann

I have a very low opinion of economic theory. I think that its survival is the result of a bait and switch where the core principles (roughtly Nash equilibrium) can’t be proven false, because they have no implications, and, given the fact that they have not been proven false, economists attempt to convince people of the joint implications of the core principles and further assumptions which are known to be false. Fortunately, very few people pay much attention to economic theory.

To continue the diatribe, the implications of economic theory as presented by right wing economists are the implications of models which are about 50 years old now. They depend on assumptions which no one claims are approximately valid. In particular, the traditional application to finance of economic theory, that is general equilibrium theory, (generically) gives the standard results only if markets are complete — that is there is a contingent claim for every conceivable contingency (including say this pays 1 unit of numeraire good if it is snowing on Mars or if Robert Waldmann stubs his toe between 6:55 EST of October 3 2008 and 7 EST).

With incomplete markets, the market outcome is generically (that is except for a set of economies with measure zero) constrained Pareto inefficient (that means that there are legal restrictions on peoples positions in financial markets which make everyone better off).

Also, there is no claim based on economic theory that financial market prices reflect fundamentals. A large set of general equilibrium economies *with complete markets* have multiple equilibria. Which equilibrium occurs is not determined by fundamentals (tastes and technology). With incomplete markets payoff irrelevant signals (sunspots) can affect prices in general (I think generically).

The conclusions of economic theory as presented by many or perhaps most economists do not follow from current economic theory, but rather from the 50 year old efforts at mathematical economic theory.

Thus the New York Times Op-ed page is not to be blamed for publishing an op-ed full of false claims about economic theory written by Mark Buchanan a physicist. I won’t excerpt, read it if you want. My objections after the jump.

Bachman has no idea what he is talking about.

First he has no idea of what economists mean when we say “equilibrium”. He just assumes that we mean stable steady state (which is what we used to mean 50 years ago). Now we mean Nash equilibrium or Walrasian General equilibrium which is nothing of the kind. He should check on recent developments in general equilbrium theory in the past 30 years. He will find the word “sunspot”. He will find that general equilbrium theorists argue that there are “equilibria” in which market prices jump around with no relevant news (based on irrelevant news that has nothing to do with tastes or technology). That is, the view of general equilibrium theorists is the exact opposite of the view Buchanan attributes to them.

He will also note that general equilibrium theorists conclude that market equilbria are generically not constrained Pareto efficient — the theorists who showed that are Herakles Polimarchakas and John Geanokoplos (hey where did I just read that name ?).

Finally the bit about how economists don’t use computer simulations is, if possible, even more wrong than the rest of the op-ed. It is like saying economists refuse to use mathematics or have no use for the theory of statistics.

I’d say that Buchanan demonstrates complete ignorance about what economic theorists have been doing in the, depending on the paragraph of the op-ed, past 30 to 50 years.

By now I’m tempted to just post my explanation of why I won’t post. I think I will.

On the other hand, while Buchanan doesn’t know anything about current economic theory, I think he does have a sense about how economic theory affects the political debate. There is a general view that, according to economic theorists, laissez faire is the best policy. Pro-market politicians are a bit reassured by this and pro-regulation and egalitarian politicians probably think they are fighting against the false prevailing economic theory. In fact, many economists argue that economic theory shows (if they are delusional about the scientific standing of economic theory) or suggests that the market is socially efficient. This is just not true at all. In particular someone who confuses “Pareto efficient” and “efficient” can claim this about markets with rational agents, perfect competition and *complete markets*. It is hard to explain what complete markets would look like, because an economy with complete markets is so totally unlike the real world. No one has ever argued that markets are approximately complete and no general equilibrium theorist has ever argued that this is a matter of less than critical importance.

The problem is, I think, that when they talk to non economists, many economists pretend that traditional economic theory is a good approximation to reality. By “traditional” I mean 50 year old. The fact that the conclusions are the result of strong assumptions made for tractability and are known to not hold without these assumptions is irrelevant. In the case of financial market equilibrium, the assumptions are not just the core assumptions of rationality and old assumptions of perfect competition but the totally crazy assumption of complete markets.

Once a model has been put in textbooks, it becomes immortal invulnerable not only to the data (which can prove it is not a true statement about the world but no one ever thought it was) but also to further theoretical analysis.

Buchanan should have talked more to Geanakoplos before shooting his keyboard off. The Times should have checked claims about current economic theory with an economist before printing them, but I think the worse problem is that economists who are also libertarian ideologues are lying about the current state of economic theory, not only its very weak scientific standing, but the fact that, even if it were all absolutely true, their policy recommendations do not at all follow from current economic theory.

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