Paul Romer na svojem blogu nadaljuje svoj pohod proti slabim makro teoretikom. Za razliko od prvega zapisa prejšnji teden je tokrat tudi uporabil bolj eksplicitne besede, denimo za nobelovca Eda Prescotta.
(za tiste, ki ne poznate ozadja: Paul Romer je začetnik teorije endogene rasti in se vsako leta omenja med možnimi kandidati za Nobelovo nagrado; njegov svetovalec pri doktoratu je bil nobelovec Robert Lucas iz University of Chicago, vendar sta se med delom na disertaciji o teoriji endogene rasti sprla, ker je Romer uporabil predpostavko monopolistične konkurence in naraščajočih donosov, Lucas pa je zahteval predpostavko popolne konkurence in eksternih ekonomij obsega. Letos januarja je na AEA srečanju ameriških ekonomistov Romer uperil prst na Lucasa, Prescotta in ostale, ki naj bi prek matematike zapekli free-market ideologijo v ekonomske modele oziroma ki z zlorabo matematike delajo slabe modele, ki so daleč od realnosti).
In his comment on my Mathiness paper, Noah Smith asks for more evidence that the theory in the McGrattan-Prescott paper that I cite is any worse than the theory I compare it to by Robert Solow and Gary Becker. I agree with Brad DeLong’s defense of the Solow model. I’ll elaborate, by using the familiar analogy that theory is to the world as a map is to terrain.
There is no such thing as the perfect map. This does not mean that the incoherent scribbling of McGrattan and Prescott are on a par with the coherent, low-resolution Solow map that is so simple that all economists have memorized it. Nor with the Becker map that has become part of the everyday mental model of people inside and outside of economics.
Noah also notes that I go into more detail about the problems in the Lucas and Moll (2014) paper. Just to be clear, this is not because it is worse than the papers by McGrattan and Prescott or Boldrin and Levine. Honestly, I’d be hard pressed to say which is the worst. They all display the sloppy mixture of words and symbols that I’m calling mathiness. Each is awful in its own special way.
What should worry economists is the pattern, not any one of these papers. And our response. Why do we seem resigned to tolerating papers like this? What cumulative harm are they doing?
The resignation is why I conjectured that we are stuck in a lemons equilibrium in the market for mathematical theory. Noah’s jaded question–Is the theory of McGrattan-Prescott really any worse than the theory of Solow and Becker?–may be indicative of what many economists feel after years of being bullied by bad theory. And as I note in the paper, this resignation may be why empirically minded economists like Piketty and Zucman stay as far away from theory as possible. …