> Let me guess - if the authors did by 5 groups the results they got were not saying something they liked. The main reason likely is that US race (treating His

> Let me guess - if the authors did by 5 groups the results they got were not saying something they liked. The main reason likely is that US race (treating Hispanic ethnicity as a race trumping nominal racial categories, so the other categories all are implicitly prefixed by “non-Hispanic”) is something like (in 5 categories): 59% White, 19% Hispanic, 13% Black, 6% Asian, 3% Other/Mixed. Or, in two categories: 59% White alone, 41% Other The two-group breakout takes far less data to get equal statistical utility for its smallest group when compared to the 5 group breakout (that's true even if you don't really care about the Other/Mixed catch-all group in the 5-group breakdown, but only the other four.)