04/06/2009 03:06 pm ET Updated May 25, 2011

McDonald's Sneak Peek at CPS 2008 Turnout Data

How did voter turnout in 2008 compare to prior years, particularly among key subgroups such as African Americans and younger voters? Some of the best data on these questions comes from the massive Current Population Survey (CPS) conducted by the Census Bureau. Every month, the Census Bureau conducts a random-sample, in-person survey of roughly 50,000 Americans. In November of every election year, they include supplemental questions on voting and registration.

The Census Bureau has not yet published their official report on 2008 voter turnout, but they released the raw data late last week and our friend Michael McDonald, the George Mason University professor who has long specialized in the study of voter turnout, did some preliminary number crunching over the weekend and has a sneak preview on his web site.

On the most anticipated questions, McDonald's analysis "confirms that African-American and youth voter turnout increased between 2004 and 2008." Specifically, the CPS shows a 4.9% increase in turnout among African Americans and 2.1% increase among citizens aged 18 to 29. Turnout among African-Americans (65.2%), which has long lagged 5 to 10 percentage points behind turnout among whites, was slightly less than a percentage point lower than turnout among whites in 2008 (66.1%).

The CPS data also essentially confirms McDonald's earlier estimate of early voting -- 29.7% of Americans told the CPS they voted early in 2008.

However, the new CPS data also produces a puzzling finding that may overwhelm the subgroup analysis once the CPS releases its official report: The overall rates of turnout and registration "declined slightly between 2004 and 2008" (from 63.8% to 63.6%). That finding is counterintuitive, at best, since the tallies from the Secretaries of State show that 9.0 million more people voted in 2008 than in 2004, while the voting age population increased by 10.1 million over the same period. Thus, McDonald concludes that "it appears almost certain that the turnout rate did not decline between 2004 and 2008 despite the statistics from the CPS" and provides this important caution:

[T]he Census Bureau's CPS voting and registration supplement is an important report that always receives major media coverage. This CPS turnout rate decline will therefore likely be uncritically reported by the media when the 2008 voting and registration report is released later in 2009. I do not believe that a turnout rate decline occurred between 2004 and 2008. While this may cast doubt on the accuracy of the 2008 CPS Voting and Registration Supplement, I would add that I believe that the data are still useful to illuminate patterns in voting and registration. Indeed, voter turnout statistics by race and age, discussed below, are consistent with patterns speculated to be present in the 2008 election. warning

McDonald has all the details on his website -- as always, his analysis is worth reading in full.

PS:  Charles Franklin promises an update soon on one of my favorite charts from 2008, his look at turnout by age using the CPS data.  Update: Franklin"s post is up