More than 97 percent of white men are married to white women, while 82 percent of black men, 65 percent of Hispanics and 48 percent of Asians marry within their own group.
The figures are based on 2005 census data analyzed by Michael Rosenfeld, a Stanford University sociologist who studies interracial marriage.
Much has been made of the difficulties black women have in selecting husbands from a pool of eligible black men shrunk by unemployment and incarceration.
Among black women age 35 and over, more than 25 percent have never been married, compared with about 7 percent of white women, census figures show.