7.2% of the population listed their ancestry as american on the 2000 census (see american ethnicity). according to the united states census bureau, the number of people in the u.s. who reported american and no other ancestry increased from 12.4 million in 1990 to 20.2 million in 2000. this change in reporting represented the largest "growth" of any ethnic group in the united states during the 1990s, but it represented how people reported themselves more than growth through birth rates, for instance, and certainly did not reflect immigration.