Exit Polls: Why They So Often Mislead

[elleng]

Did you think John Kerry was poised to win the presidency? That Scott Walker was close to losing the 2012 governor’s recall election in Wisconsin? Do you believe that the black share of the electorate in North Carolina dropped to 23 percent in 2012, from 26 percent in 2004?

If you said “yes” to any of those things, you probably have too much faith in exit polls.

Don’t get me wrong: Exit polls are an exciting piece of Election Day information. They’re just not perfect. The problem with them is that most analysts and readers treat them as if they’re infallible.

The problems begin early on election evening, when the first waves of exit polls are invariably leaked and invariably show a surprising result somewhere. You’re best off ignoring these early returns, which are unweighted — meaning the demographic mix of the respondents is not adjusted to match any expectations for the composition of the electorate. The first waves also don’t even include all of the exit poll interviews.

The problems continue with the final waves, which analysts pour over in the days after the election and treat as a definitive account of the composition of the electorate. Some foolish journalists might write entire posts that assume that the black share of the electorate was 15 percent in Ohio. In reality, the exit polls just aren’t precise enough to justify making distinctions between an electorate that’s 15 percent black and, say, 13 percent black.

The imperfections of the exit polls are not hard to show. Here are two quick examples, based on official voter turnout statistics:

http://www.nytimes.com/2014/11/05/upshot/exit-polls-why-they-so-often-mislead.html?hp&action=click&pgtype=Homepage&module=b-lede-package-region&region=top-news&WT.nav=top-news&abt=0002&abg=1

[musicblind]

1. Really interesting read. Thanks for sharing that! n/t