Thursday, 26 August 2004

Explanation, prediction, and the Fair model

There’s been some discussion of late of Ray Fair’s model, and particularly its prediction that George Bush will walk away with 57.5% of the two-party vote in November. Bill Hobbs and Don Sensing find this to be interesting—and, at some level, I suppose it is. But I have to mention a couple of caveats:

  1. I seriously doubt either major-party candidate will get 57.5% of the two-party vote. A few numbers for comparison: Ronald Reagan’s landslide in 1984 against Walter Mondale netted 59.2% of the two-party vote, while Bill Clinton’s pounding of Bob Dole got 54.7% of the two-party vote. I’d frankly be surprised if Fair’s forecast is even correct within his stated margin of error (±2.4%). To be gracious to Fair on this point, he does candidly acknowledge that there could be specification issues that would inflate the forecast.
  2. I think forecasting models do a poor job of explaining the causal mechanisms that take place. The national economy doesn’t vote—rather, about a hundred million Americans do, and the effects of the national economy on individuals are for the most part weak (but, admittedly, can be quite strong for voters in particular industries and regions).

Of course, a third caveat is that forecasting the national vote-share is (in my opinion) a misspecification of the institutional conditions under which the election takes place; there are 51 elections (in the 50 states and District of Columbia) that allocate representation in the electoral college, and I generally think that understanding those 51 elections is much more important than forecasting the headline figure, which only has a tenuous relationship with the substantively meaningful outcome (who wins the election).

Also (potentially) of interest: back in my slightly-more-prolific days, I posted a brief exposition of my distaste for (and disinterest in) election forecasting models.