Medicine and microfoundations hegemony in macroeconomics

August 25, 2017

Mainly for economists

I’m beginning to think I should have made much more of analogies between economics and medicine in discussing what I call the microfoundations hegemony: the idea that the only ‘proper’ macroeconomic models are those that have all their equations consistently derived from microeconomic theory. The analogy I have in mind is that biology represents microfoundations, and statistical analysis linking, say, smoking to lung cancer are the non-microfounded models. (I’ve used the analogy in other contexts.)

I was thinking about this in the context of a paper I have just finished which uses a diagram that Adrian Pagan used to describe different types of macromodels. The diagram, which you can find in an earlier post, has ‘degree of empirical coherence’ and ‘degree of theoretical coherence’ on the two axes. Particular macromodels can be placed within this space. At one extreme involving the highest theoretical coherence but weaker empirical coherence are microfounded DSGE models. At the other are VARs: statistical correlations between a group of macro variables with no theory-based theoretical restrictions imposed. In the middle are what I call Structural Econometric Models and Blanchard calls Policy Models, which use an eclectic mix of theory and econometric evidence.

If you have a simple view of the hard sciences, this diagram looks very odd. Theories either fit the facts or they do not. But I think a medic could make sense of this diagram by thinking about medical practice based on biology (for example how cells work and interact with various chemicals) and practice based on epidemiological studies. Ideally the two should work together, but at any particular moment in time some medical ideas may borrow more from one side or the other. In particular, statistical studies could throw up links which do not have a clear and well established biological explanation.

Now imagine the microfoundations hegemony in macroeconomics applied to medicine. Statistical longitudinal studies in the 1950s showed a link between smoking and lung cancer, but the biological mechanisms were unclear. The microfoundations hegemony applied to this example who mean that medics would argue that until those biological mechanisms are clearly established they should ignore these statistical results. The investigation of such mechanisms should remain a top research priority, but for the moment advice to patients should be to carry on smoking.

OK, that is perhaps a little harsh, but only a little. That some macroeconomists (Icallthem microfoundations purists) can argue that you should model and give policy advice based not on what you see but on what you can microfound represents something that I cannot imagine any philosopher of science taking seriously (after they had stopped laughing).        

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