Not to say that this proves anything in particular, but it is important (especially if you are, say, a social studies teacher) to note, as Matt does, that Americans of all stripes tend to be way, way off in their perception of the current racial breakdown of the US. Specifically, we tend to significantly underestimate the percentage of white people and overestimate the number of minorities. Try it with your classes (I used to).
For example, in this poll, over 40% of people think blacks make up more than 30% of the population, when in fact they are only 12% or so. White people are still around 70%. While on one level race doesn't exist, it is just a construct, etc., I do think this mis-perception has all kinds of weird and subtle distorting effects on how people understand the political facts on the ground in this country.