Wednesday, December 03, 2008

AS, AD, and the New Deal

Paul Krugman has posted a nice note analyzing New Deal wage policies using the model of aggregate supply and aggregate demand familiar to teachers of undergraduate macroeconomics. The essence of Paul's argument is that the economy of the Great Depression was in a liquidity trap, which implies that the AD curve is vertical, which in turn implies that policies that adversely shift the AS curve do not affect equilibrium output in the short run. Thus, a policy that under normal circumstances would be bad, such as cartelizing the supply of labor, is not bad under the extraordinary circumstances of the 1930s. (See Gauti Eggertsson for a more sophisticated version of this line of argument.)

Even staying within the AD-AS model, it seems possible to argue the opposite point of view. Imagine you are a manager of a firm considering a long-term investment project. The President has just announced a policy to encourage your workers to form a cartel. How does that influence your decision to proceed with the project? Very likely, it deters you. Investment spending, however, is part of aggregate demand (in fact, one of the most volatile components). Thus, the policy could shift the AD curve, as well as the AS curve, in a contractionary direction.

As a general matter, the state of aggregate demand depends on an amorphous variable called confidence. Anything that threatens to screw up AS in the long run most likely reduces confidence and AD in the short run. The textbook separation of AD and AS is useful for focusing discussion in the undergraduate classroom, but events in the real world are rarely so clean.