Sailer only really gets into trouble when he tries to explain the disparity. Searching for correlated variables, he happens upon muscularity. Using the percent body fat goal as determined by a TV fitness expert as his proxies, he notes that the ratio between differences in body fat goals for various pairings. To get the flavor of his methodology, the difference between black men (12%) and white women (22%) is 10%, while the difference between white men (15%) and black women (19%) is 4%. This 10:4 ratio is almost an exact match to the 72:28 ratio in marriage rates. And the ratio for white-Asian marriages is also 10:4, matching their 72:28 marriage ratio as well. Thus, Sailer concludes:
When, in the names of freedom and feminism, young women listen less to the hard-earned wisdom of older women about how to pick Mr. Right, they listen even more to their hormones. This allows cruder measures of a man's worth -- like the size of his muscles -- to return to prominence. The result is not a feminist utopia, but a society in which genetically gifted guys can more easily get away with acting like Mr. Wrong.
This is certainly thought-provoking, and like any concatenation of correlations, may contain some truth. But we should not imagine that it is too scientific. For starters, body fat goals are not the same as body fat. Are blacks actually more muscular than whites? Sailer has no idea, or if he does he doesn't say. Are black men in black-white marriages typical of all black men? (And for that matter, are the white women typical?) The same questions apply to white-Asian pairings, of course. And of course, Sailer does not (and really cannot, given the data he has to work with) tackle the gap between correlation and causation that so hampers amateur investigation.
Even with all these shortcomings, an interested social scientist could use Sailer's ideas as a jumping-off point for actual scientific study. If we had any interest in such things, perhaps one might.