martes, 13 de marzo de 2012

Las encuestas en el Sur Profundo suelen ser poco fiables

Nate Silver:
Polls in these states have a pretty awful track record.

If you had looked at the Real Clear Politics average of polls in Alabama in advance of the 2008 primaries, for instance, you would have called the Republican and the Democratic races wrong. Hillary Rodham Clinton had a nominal advantage in the Democratic race there, leading in the Real Clear Politics average by about one percentage point. But in fact, Barack Obama won. It wasn’t even close; he carried the state by 14 percentage points.

A similar problem was evident on the Republican side. The polls were wildly divergent from one another — showing everything from a 16-point lead for Senator John McCain to a 9-point advantage for Mike Huckabee. But the average put Mr. McCain about four percentage points up in Alabama. Mr. Huckabee won the state by about four percentage points instead, however.

Alabama and Mississippi haven’t played an important role in primaries that often, but in one important prior case — the Democratic race in 1984 — the polls were also pretty bad there. Surveys substantially overestimated Walter Mondale’s standing — one survey had him with as much as 48 percent of the vote, but he got just 35 percent. They had Gary Hart finishing about 10 percentage points ahead of Senator John Glenn for second place, when the two candidates about tied for second. And Jesse Jackson did substantially better than was forecast for him by the polls.