In 2010, 9 million Americans identified themselves as having more than one race, a 32 percent increase from 2000. The number who define themselves by a single race increased by 9.2 percent. The 2000 survey was the first time the census allowed people to self-identify as more than one race.
Four specific combinations made up the bulk of the increase: white and black (1.8 million), white and "some other race" (1.7 million), white and Asian (1.6 million) and white and American Indian and Alaska Native (1.4 million).
The Census lists five race categories: black, white, Hispanic, Asian, American Indian and Alaska native and native Hawaiians/Pacific Islanders. It also allows respondents to select the box "some other race."