Monday, October 13, 2008

Krugman wins Nobel

Has it been a year already? Two years?

As before, the best writeups are on Marginal Revolution.

Alex Tabarrok:
Consider the simplest model (based on Krugman 1979). In this model there are two countries. In each country, consumers have a preference for variety but there is a tradeoff between variety and cost, consumers want variety but since there are economies of scale - a firm's unit costs fall as it produces more - more variety means higher prices. Preferences for variety push in the direction of more variety, economies of scale push in the direction of less. So suppose that without trade country 1 produces varieties A,B,C and country two produces varieties X,Y,Z. In every other respect the countries are identical so there are no traditional comparative advantage reasons for trade.

Nevertheless, if trade is possible it is welfare enhancing. With trade the scale of production can increase which reduces costs and prices. Notice, however, that something interesting happens. The number of world varieties will decrease even as the number of varieties available to each consumer increases. That is, with trade production will concentrate in say A,B,X,Y so each consumer has increased choice even as world variety declines.
Krugman (1991) (JSTOR and here) brings increasing returns together with capital and labor migration and transport costs into one model. Krugman's (1991) model has become a workhorse of economic geography and international trade. The model is too complex to explain here but the reasons for that complexity are clear to see - when everything becomes "endogenous" small initial differences can make for big effects. To minimize transport costs, for example, firms want to locate near consumers but consumers want to locate near work! Thus, there are multiple equilibria and at a tipping point the location decisions of a single firm or consumer can snowball into big effects. So Krugman has been a leader in introducing tipping points, network effects and thus the importance of history into international trade as well as into economics more generally.
It is pleasant to see how economists and bloggers, regardless of political preferences, seem to applaud this choice: Mankiw, Brian Caplan, Will Wilkinson, Steve Levitt.

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