Answer formats in British census and survey ethnicity questions: Does open response better capture 'superdiversity'?.

During a period of unprecedented ethnicity data collection in Britain, an almost universal characteristic of this practice has been the mandated use of the decennial census ethnicity classifications. In Canada and the USA a greater plurality of methods has included open response, now recommended for the 2020 US Census. As the ethnic diversity of Britain has increased, driven by immigration dynamics and population mixing leading to ‘superdiversity’, the census is no longer able to capture the new populations. The validity and utility of unprompted open response is examined in several ‘mixed race’ datasets. It is argued that open response can be a modus operandi for large-scale ethnicity data collection and that the lack of consistency in recording of such responses need not necessarily be viewed as a drawback. Open response offers substantial insights into the country’s superdiversity in a way that ethnicity categorization alone cannot.