A questioner below was curious if vocabulary test differences by ethnic and region persist across income. There's a problem with this. First, the INCOME variable isn't very fine-grained (there is a catchall $30,000 or greater category). Second, it doesn't seem to control for inflation. But, there is a variable, DEGREE, which asks the highest level of education attained. I used this to create a "college" and "non-college" category (i.e., do you have a bachelor's degree or not). Because of sample size considerations I removed some of the ethnic groups, but replicated the earlier analysis.
Below are two tables. One shows the mean vocab score for region and ethnicity (for whites) for those without college educations, and another shows those with college educations. I decided to generate a correlation over the two rows, even though it sure isn't useful as a quantitative statistical measure because of the small number of data points. Rather, I just wanted a summary of the qualitative result. The short answer is that the average vocabulary difference seems to persist across educational levels (the exception here is the "German" ethnicity).