Every five years, the national Census of Population and Housing provides a window on the demographic, social and economic characteristics of Australia's Indigenous population. In line with each census count of Indigenous Australians since 1971, when a question on self-identified Indigenous origins was introduced, the 2001 count produced an intercensal change in numbers that cannot be explained by demographic processes alone. There is evidence of a highly systematic movement of people into the census-identified Indigenous population in 1996, and out of the population in 2001. This is suggestive of procedural or processing change, as much as anything else.