And following-up on my post this morning on the demographics for the North Carolina polls, here is the same set of statistics, when available, for the recent surveys of Indiana. Since African-American's are a much smaller share of the population in Indiana, the Clinton-Obama results are not quite as sensitive to their percentage of the Democratic electorate as in North Carolina. However, should the Indiana result be close, the size of the African-American population will be important. Also, the tables show that the polls vary on age as much as in other states.
The following table shows demographic composition statistics for those pollsters that have released them. Click on the table to display a larger version that also includes the vote preference results for reach poll.
The table excludes statistics from pollsters that have not publicly released demographic information for their North Carolina surveys (or perhaps more accurately, have not published anywhere I could find it): LA Times/Bloomberg, Indianapolis Star/WTHR/Selzer, Howey-Gauge (and thanks again to Pollster reader jac13 for sharing the demographic profile data that Zogby makes available to paid subscribers).
In Indiana we see the same wide variation in the age distribution among pollsters seen elsewhere: Even The percentage of 18-to-29-year-olds varies from 8% to 22%, the percentage 18-to-44 varies from 26% to 51%.
With the exception of one pollster, the variation in racial composition is smaller. Most show an African-American percentage of somewhere between 9% and 12%, with Research2000 (13%) and Suffolk University (15%). The most extreme value is the Howey-Gauge survey, which reported a much higher percentage of African-Americans (20%) among likely primary voters.
Brian Schaffner noticed last week that larger percentage of African-Americans in the Howey-Gauge poll explained how they showed Obama with a two-point advantage while other firms showed Obama trailing by seven or more percentage points. He has some interesting speculation about the composition of the Indiana electorate, but ultimately I have to agree with his bottom line conclusion: Given the lack of an Indiana benchmark for past Democratic presidential primaries, "we don't really know what to expect in terms of African American turnout."
[Updated table to include new surveys from PPP and InsiderAdvantage]