Uma anedota popular em economia diz que só há duas economias: a microeconomia e a má economia, numa crítica explícita à falta de fundamentos da macroeconomia. Simon Wren-Lewis, que tem escrito algumas das coisas mais interessantes acerca de modelização, volta hoje a criticar a ideia de que só alicerces macroeconómicos dão solidez à macro. Arguments for ending the microfoundations hegemony, no Mainly Macro, fornece cinco boas razões, das quais cito apenas duas.
1) Empirical evidence. There may be strong empirical evidence in favour of an aggregate relationship which has as yet no clear microfoundation. A microfoundation may emerge in time, but policy makers do not have time to wait for this to happen. (It may take decades, as in the microfoundations for price rigidity.) Academics may have useful things to say to policy makers about the implications of this, as yet not microfounded, aggregate relationship. A particularly clear case is where you model what you can see rather than what you can microfound. For further discussion see this post.2) Complexity. In a recent post I discussed how complexity driven by uncertainty may make it impossible to analytically derive microfounded relationships, and the possible responses to this. Two of the responses I discussed stayed within microfoundations methodology, but both had unattractive features. A much more tractable alternative may be to work directly with aggregate relationships that appear to capture some of this complexity. (The inspiration for this post was Carroll’s paper that suggested Friedman’s PIH did just that.)