Another Pollster Thinks Youth Are Undercounted

At FiveThirtyEight.com, Nate Silver notes that another pollster - Selzer & Co - think that most polling outfits are undercounting and improperly weighting the youth vote in their polls, resulting in a net gain in support for John McCain:

Selzer thinks that a lot of pollsters may be undercounting the youth vote, and potentially also the black vote. Young voters are becoming harder and harder to reach. They are in the habit of screening their phone calls. More problematically still, a great number of them (roughly 50 percent of voters under 30) rely principally or exclusively on cellphones, which most pollsters (including Selzer) will not call.

Pollsters can attempt to work around this problem by weighting the young voters they are able to reach more heavily; indeed, it is imperative that they make at least some attempt at weighting if they want to produce accurate results. But Selzer says she knows of at least one prominent polling firm -- she would not mention them by name -- which is not weighting by age groups at all.

Moreover, many of the pollsters that do weight by age group may be doing so -- to her mind -- in the wrong way. Specifically, they tend to use the 2004 election as a benchmark, when 17 percent were aged 18-29. Selzer uses census bureau data as her benchmark instead; among American adults aged 18 and up, about 22 percent age 18-29. This might not seem like a large difference, but given Obama's strong performance among young voters, it makes a difference of about 1.5 points in the net Obama-McCain margin.

This comes on the heals of a report by Pew Research, and previous blog posts from Mark Blumenthal and Nate Silver, noting a consistent 2 - 3% advantage for McCain in polls that exclude cell-only samples that heavily favor voters under 30 and are more pro-Obama than landline users of all ages.

Selzer is attempting to compensate, resulting in a consistent variance in favor of Obama between her polls and other pollsters. Silver notes that this is a gamble, but one that could pay off. She nailed the prediction for the Iowa Caucus, and if she's equally accurate in November, he predicts that we could see a whole lot more pollsters start to change their methodology.