MBM review of the ONS paper ‘Methodology for decision making on the 2021 Census sex question concept and associated guidance’

MBM review of the ONS paper ‘Methodology for decision making on the 2021 Census sex question concept and associated guidance’

Less than six weeks before the date of the 2021 census in England and Wales, the Office for National Statistics (ONS) published the guidance which
will accompany the compulsory sex question. The guidance is of critical importance because it defines what is meant by ‘sex’.

The finalised ONS guidance advises: ‘If you are considering how to answer, use the sex recorded on one of your legal documents such as a birth certificate, Gender Recognition Certificate, or passport’. This means that the definition of sex in the next census will conflate three separate demographic categories. These are: biological sex; legal sex (for those who have acquired a Gender Recognition Certificate and who may or may not have changed the sex marker on their birth certificate); and selfdeclared gender identity or gender reassignment (for those who do not have a GRC, but have changed the sex marker on their passport or other unspecified legal documents). It will not be possible to disentangle the data across these three categories.

To justify this approach, the ONS has produced a methodological paper that outlines how it reached its final decision (hereafter ‘ONS paper’). This was
presented to Methodology Assurance Review Panel (MARP) on the census, the Chair of which wrote to the Chief Statistician Professor Sir Ian Diamond in
November 2020 seeking clarity about the decision-making process in relation to the sex question guidance.

This briefing considers the findings in the ONS paper. We also examine the available findings from a piece of qualitative research, undertaken by ONS in
late 2020, which the ONS paper draws upon. Together with our wider body of research and analysis in this area, we argue that:

  • ONS has not fully engaged with the substantive arguments as to why data on biological sex is important, nor demonstrated why robust data on biological sex is no longer needed.
  • ONS has not provided evidence to suggest a balance of views between expert population data users who require data based on biological sex, and those who require data on ‘self-identified’ sex.
  • The consultation process on the sex question guidance has been partial, privileging particular views over others and lacking in transparency. This was also the case in the 2001 and 2011 census.
  • The ONS’ conclusions on response rates rely on unpublished, nonrepresentative qualitative research, involving 52 purposively selected participants, undertaken at a very late stage in the decision-making process.  This research did not test the option that ONS have chosen.
  • ONS state that collecting data on biological or legal sex is likely to adversely affect response rates due to the perceived invasion of privacy. No robust research evidence is provided to support this conclusion, nor do the ONS acknowledge recent formal legal opinion in this area.
  • ONS have not addressed the key concerns raised by expert data users in relation to data reliability for sub-groups.
  • ONS’ conclusions on continuity and comparability rely on the flawed and ahistorical assumption that self-reported sex is synonymous with ‘self-identified’ sex, and that all previous censuses therefore recorded ‘self-identified’ sex.
  • Editing and imputation rules in the 2001 and 2011 censuses show that in both years, ONS treated responses to the sex question as legal sex, and not ‘selfi-dentified’.
  • The most significant break in continuity is likely to occur in 2021, as a result of the proposed ONS guidance.
  • ONS’ approach to equality monitoring does not appear to recognise that the onus is on public authorities to collect data that is aligned with the Equality Act 2010.
  • As the UK’s gold standard data collection exercise, the sex guidance in the census will adversely affect other surveys, including medical and biological
    research, where there is already evidence that public authorities are shifting away from collecting data on biological sex.