www.telegraph.co.uk/news/2022/04/27/snp-abandons-census-deadline-quarter-scots-fail-respond/
'Extending the window for responding raises worrying questions about data quality,” Lindsay Paterson, professor of education policy at the University of Edinburgh, said. “In normal social surveys, there are strict quality controls on the time given to respond. “This is because people vary in how they respond, especially for opinion questions such as the several identity questions in the census. For example, how people answer the question about gender identity might vary according to whether some controversy about gender identity is in the news. The same is true of national identity and ethnic identity.” He added: “As a social statistician, I would not use census data on identity that had such an arbitrarily varying window of replying.”'