For the Weekend: July 27, 2012: Free as in Beer, Free as in Speech, Free as in Ours Department
Weekend Musings Triggered by Observing That Noah Smith Is Working Hard to Make John Cochrane Appear Less Clueless About the World than He Is...

Noahpinion: What If You Have Garbage Microfoundations?

Noah Smith:

Noahpinion: Why bother with microfoundations?: [W]hat we call “microfoundations” are not like physical laws. Heck, they’re not even true. Maximizing consumers are just a metaphor, possibly useful in making sense of behavior, but possibly not. The metaphors we use for microfoundations have no claim to be regarded as representing a higher order of truth than the ad hoc aggregate metaphors we use in IS-LM or whatever…. Using wrong descriptions of how people behave may or may not yield aggregate relationships that really do describe the economy. But the presence of the incorrect microfoundations will not give the aggregate results a leg up over models that simply started with the aggregates…. When I look at the macro models that have been constructed since Lucas first published his critique in the 1970s, I see a whole bunch of microfoundations that would be rejected by any sort of empirical or experimental evidence….

Macroeconomists seem to have basically nodded in the direction of the Lucas critique and in the direction of microeconomics as a whole, and then done one of two things: either A) gone right on using aggregate models, while writing down some "microfoundations" to please journal editors, or B) drawn policy recommendations directly from incorrect models of individual behavior.

Brad DeLong puts this rather more pithily:

I now have the most bizarre image in my mind: A seminar at the Library of Alexandria in 300 A.D., with an astronomer trying to provide micro foundations in the form of calculations of how large their wings must be and how fast their wings must beat for the angels to push the planets on their tracks through the quintessential spheres…