The Forbes 400 is the most fun of the many rankings published by magazines these days, because individuals rapidly ascend and descend due to changes in fortune. In contrast, most of the other lists are forced to generate some excitement by arbitrarily changing their standards. For example, the US News and World Report list of top universities would be wholly stagnant if they didn't constantly shuffle their rules. For example, one year Cal Tech suddenly vaulted to #1, because the editors had changed the rules to benefit Cal Tech. The next year, Cal Tech had dropped considerably because the rules were changed again. Similarly, Golf Digest's Top 100 Golf Courses list has always featured Pine Valley as #1, except for brief periods when they fiddle with the methodology.
But the Forbes 400 is fun each year, because people really do rise and fall while the methodology stays the same. For example, casino king Sheldon Adelson came out of nowhere to peak at #3 in 2007, but is now down to 26.
But that turnover makes comparisons of two separate years a little tricky because different sectors come in and out of fashion. Nonetheless, comparing Nathaniel Weyl's ethnic breakdown of the 1987 Forbes 400 to one based on Jakob Berkman's work on the 2009 Forbes 400 seems reasonable. Race / History / Evolution Notes has the 1987 and 2009 figures here.
For example, Italians are up and Armenians are down. (Keep in mind that these are just estimates, and there are lots of complications in the way of coming up with perfect counts.)