Growth in the Indigenous population between the 2011 and 2016 Censuses was much faster than would be predicted by our best estimates of fertility and mortality. Part of this faster than projected growth came from a larger number of people who identified as Indigenous in 2016 but not in 2011, compared to those who identified as Indigenous in 2011 but not 2016. That is, there was a net increase in the population due to identification change. In this paper, we use a new dataset – the Australian Census Longitudinal Database – to analyse the characteristics of this identification change, as well as the implications for our understanding of changes in socioeconomic outcomes.