Knowing and Making

There has been much talk about microfoundations on the economics blogs in the last few months [ Noahpinion , Mark Thoma , Simon Wren-Lewis   twice , Andrew Gelman   twice , Karl Smith , Paul Krugman   twice , Robert Waldmann , Rajiv Sethi from 2009 ]. The idea of microfoundations is that a model of the overall economy should be consistent with how individual people act. The aggregate behaviour of variables like GDP, government deficits and unemployment should be derived by adding up the choices of individuals, not by treating the whole population as if it were a single entity. (A microfounded model might start off like this: "Imagine N agents, each of which has income y n , consumes c n and saves s n . Then y n = c n + s n . For each agent, s n varies with the interest rate r according to the following relation..." while a non-microfounded model is more likely to start: "Total spending in the economy is C and saving is S. C+S must sum to Y, total income. S varies w...

[ Apologies to X-Factor fans: this article is about "one direction" towards a new model of macroeconomics, not about the band. But do feel free to stick around and join in the discussion. ] If you read nothing but Rajiv Sethi 's and Interfluidity 's blogs, and developed all the consequences of what they said, you'd get a spectacular career in economic research out of it. Fortunately, Mark Thoma reads them - as well as hundreds of others - and has a good commentary on a recent post of Rajiv's . I won't quote the whole thing, but here is the key message. Without the assumption of a representative agent - the idea that everyone in the economy behaves identically - current macroeconomic models can't work. But this assumption misses some of the key dynamics in the economy - the fact that some people borrow and others save; the fact that different people have different beliefs and preferences - which are fundamental to both why and how economic activity...