By the 2000 census, demographic changes including the end to slavery, immigration from Europe and Asia, assimilation of multiracial persons, and other factors resulted in a population in which 6.2% of the population identified as black, 40% as pardo, and 55% as white. Essentially most of the black population was absorbed into the multi-racial category by intermixing. A 2007 genetic study found that at least 29% of the middle-class, white Brazilian population had some recent (since 1822 and the end of the colonial period) African ancestry.