What kind of mixed race/ethnicity data is needed for the 2020/21 global population census round: the cases of the UK, USA, and Canada

In western countries the mixed race/ethnicity population is experiencing a rapid increase in numbers and growing diversity, raising challenges for its capture in censuses and surveys. Methods include exact combinations of interest, multi-ticking, and open response, as exemplified by the censuses of England and Wales, the USA and Canada, and Scotland and Northern Ireland, respectively. However, investigations of question face validity, reproducibility of findings, and efficacy of capture reveal quality problems with all three approaches. The low reporting reliability of this population urgently requires research and testing to identify optimal strategies. While there is clearly no one gold standard method of capture and current approaches have developed within national contexts, it is timely to review these methods across the three countries and to make recommendations for the upcoming 2020/21 censuses.