Dear William,

Thank you for your letter of 14 June 2022 regarding census response rates in Scotland and the implications for the integrity of UK-wide data. I will answer your specific questions in turn, but first I wanted to emphasise the close working relationship between all UK Census offices. We have offered and provided support to National Records of Scotland (NRS) including sharing designs, seconding staff, and are now working with them to develop methods to maximise the accuracy of their Census estimates.

The Office for National Statistics (ONS) also worked with NRS to establish an international steering group, which is providing the highest quality technical expertise, advice and challenge to NRS on census matters. This group is advising NRS to focus efforts toward a good census coverage survey, particularly in regions where responses were lowest, and strengthen the use of administrative data to supplement census data sources in their statistical production, including a clear steer to prioritise the early acquisition of new administrative data sources. This oversight will offer NRS the best possible opportunity to deliver a high-quality outcome for Scotland that will, in turn, contribute to high-quality UK statistics.

The ONS has committed an internationally renowned team of experts equipped with decades of demographic experience to work alongside NRS. Through a combination of this world-leading expertise, the ambitious use of supplementary administrative data, and sophisticated estimation methods, I remain confident that together we will deliver robust UK-wide estimates of the population.

What assessment has been made of the reasons underlying the low response rate in certain areas, and what steps were taken to avoid this occurrence? To what extent is the separate delivery of the Scottish Census considered to have impacted the response rate?

The Census in Scotland is a devolved matter; our assessment of the reasons underlying a low response rate in some areas and the associated mitigations has therefore been formed through our close working partnership with NRS.

The decision by Scottish Ministers to move Scotland’s Census to March 2022 was informed by NRS analysis of the potential impact of COVID-19 on the quality of an operation in March 2021. NRS adopted a diverse and inclusive approach to public awareness around census through media and physical advertising, follow-up reminders, field staff, and focused efforts in areas of low return; approaches comparable to those of the ONS and the Northern Ireland Statistics and Research Agency (NISRA). Evidence gathered in Scotland at the end of the collection phase reported that ‘too busy’ and ‘not aware of the Census or the need to complete it’ were the more common reasons given by householders who had yet to return.

As already mentioned, in light of lower than anticipated returns, the ONS and the Registrar General for Scotland established an international steering group of census and coverage experts. Despite these challenges in the collection phase, having considered the position and the planned next steps with the census in detail, the steering group have confirmed that there is a stable foundation from which to move
from census collection onto the next stage of the census operation, namely the census coverage survey and the incorporation of administrative data into estimates. It is the combination of census returns, coverage survey, administrative data, and estimation methodology that will deliver high quality census outputs for Scotland.

What are the implications of Scotland’s lower response rate for the quality and comparability of UK-wide population statistics?

By taking the actions outlined above, through a combination of census data, supplementary administrative data, and sophisticated estimation methods, we believe that it will be possible to deliver a high-quality outcome for Scotland that will, in turn, contribute to high-quality UK-wide population statistics.

What actions will be taken to quality-assure the Scottish Census data in order to reduce the impact of the lower response rate on the standards of UK-wide population statistics?

NRS remain committed to continuing to produce the best possible population estimates for Scotland, which will be used to produce UK-level population estimates. They currently produce annual official population figures for Scotland using data from a range of sources including the Census, registration data on births and deaths, migration estimates, and a wide range of other administrative data sources. NRS continue to improve these statistics through augmentation of existing and new administrative data sources, ensuring the focus is to deliver population estimates that are accessible and valuable for users.

NRS continue to work closely with partner organisations across the UK, including the ONS and NISRA, to ensure that UK population data and analysis is coherent, comparable and understandable for all users across the UK.

The Committee might also wish to note that the Office for Statistics Regulation (OSR) is currently assessing the Scottish Census, including how NRS are responding to the current situation and the methods and quality assurance they will put in place to provide the best quality data and statistics on the population of Scotland. The OSR has, in both its preliminary findings assessment report for Censuses in the UK, and in subsequent assessment reports for England, Wales and Northern Ireland, highlighted UK data and continues to engage with all three census offices in this regard. I am sure the Director General for Regulation, Ed Humpherson, will keep the Committee informed of its findings, which it plans to publish in November.

Yours sincerely,
Professor Sir Ian Diamond