I liked reading 538.com during the election season as much as anyone, and still think it’s an insightful site with a lot of interesting things to say. That said, I’ve been kind of surprised by the post-election surge of praise for Nate Silver. You would think, based on some of the commentary, that his innovative and complicated formula wound up giving us some incredible insight we couldn’t have gotten from anywhere else. In fact, though the 538 algorithm performed pretty well, the core reason it performed well was that crude polling averages are very accurate in US Presidential elections:
Assuming that Obama will win by 7.1%, the Pollster.com regression line of all national polls was only off by only 0.5%. The same can be said for the simple mean of national polls performed by Real Clear Politics. The lesson here is that when there are a high number of public polls, election forecasters are not very useful. Even a schmo like me can just conduct a simple mean of all the polls, and come pretty close to the final result.
The high stakes in US Presidential elections make people feel a lot of anxiety about outcomes. This makes people very interested in the subject of election forecasting. And they would like their level of interest to be matched by the forecasting process itself being interesting. But in fact the large number of public polls on something like a presidential election makes the outcomes quite easy to forecast based on crude measures. What’s more, even absent polling, Presidential election outcomes seem to be pretty predictable based on nothing more than macroeconomic variables. But even if you don’t believe in the fundamentals, the reality is that “the polls,” in the aggregate, are very accurate and there’s not much more to it. For other things, like primary elections in states that have rarely held competitive primaries (and this is where 538 initially made a name for itself), or in little-polled House races, there’s lots of room for other methods. But presidential elections are easy.