Saturday, July 14, 2012

Why Are So Many Pollsters Oversampling Democrats?

My regular correspondent Number-Cruncher checks in, groaning about the latest Pew poll and that organization’s strange habit of including an unrealistic percentage of Democrats in their sample.

The latest one from Pew poll is a shining example of why our side gets so frustrated with polls. Every time a Pew poll comes out, the numbers appear out of whack. Of course if you are a number-cruncher and look to the cross-tabs, the results are clearly flawed. Pew, to its credit, tells us its history since 1988. Basically in 1988 they did a good job, calling the race almost perfectly, possibly even overestimating Bush support by 0.4% (keep in mind they round so 50-42 could be 7.6%). But since then, their results have been downhill.

Starting in 1992, EVERY Pew poll appears to lean to one directionalways towards the Democrat, and by an average of more than 5 percentage points. Worse this is a reflection of the “final” poll which even the Democratic firm, Public Policy Polling, usually gets right.

October 1988 — Bush 50 Dukakis 42; Actual Result Bush +7.6 (Call this one spot on.)

Late October 1992 — Clinton 44 Bush 34; Actual Result :Clinton +5.5 (Skew against Republican candidate +5.5)

November 1996 — Clinton +51 Dole 32; Actual Result Clinton +8.5 (Skew against Republican candidate +10.5)

November 2000 — Gore 45; Bush 41 (Skew against Republican Candidate +3.5)

November 2004 — Kerry 46; Bush 45 (Skew against Republican Candidate +3.4)

November 2008 — Obama 50 McCain 39 (Skew against Republican + 3.8)

After being wrong in the same direction so consistently, wouldn’t you think that Pew might attempt to adjust their sampling techniques to adjust their techniques to avoid under-sampling Republican voters?  Keep in mind the polls I have highlighted are the last polls in the race.  I find it interesting that not one of their poll statisticians came out and said, ‘Boss, these results look whacked out because the electorate is going to be more than 24 percent Republican, and self-identified Democrats aren’t going to outpace Republicans by 9 percentage points.’  The Democrats couldn’t even reach that margin in 2008 . . . and you wonder why so many people think Obama is going to win.  Didn’t Einstein once say the definition of insanity was “doing the same thing over and over again and expecting different results”.  So I ask are the people at Pew insane or just biased?

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