According to the conventional wisdom, blacks are more violent than whites because of poverty. Researchers, who are supposed to get beyond the cliches, have rarely tested this idea, and it doesn't help that the relevant data is scarce.
The National Couples Survey asked married people (N = 1,181) if they had ever had a "physical argument." I limited the sample to respondents who had graduated high school--but who had gone no further--in order to eliminate variation in social class. Here are the percentages saying there has been physical fighting in the marriage:
American Indians 20.0
* p < .05, two-tailed test, compared with whites.
Married blacks at the same level of education as whites are almost 3 times more likely to be violent. Hispanics are more than twice as likely. Sample sizes are so small, the Asian/white and Amerindian/white differences are not significant.