Dear Roger
Use of COVID-19 prevalence rates by Scottish Government
On 3 July First Minister Nicola Sturgeon in her COVID-19 speech, claimed that the prevalence of the virus in Scotland is five times lower than it is in England. The sources used to underpin this claim have been difficult to identify. The explanation provided to my team at the Office for Statistics Regulation was not clear. You have now explained to us that the Scotland prevalence figure was sourced from the Scotland’s COVID-19: modelling the epidemic (issue no.6) 25 June and the England prevalence figure was sourced from modelling work done by the London School of Hygiene and Tropical Medicine, using a UK estimate as a proxy for England. The UK estimate for the dates in question was not published and was provided to you to allow for this comparison. A UK prevalence figure is available on the London School of Hygiene and Tropical Medicine website however this is a real-time report with an unclear update schedule.
As the UK/England prevalence rate was not available publicly, we understand that you then compared the upper prevalence rates published in Scotland’s COVID-19: modelling the epidemic (issue no.6) 25 June and the Office for National Statistics’ COVID-19 Infection Survey pilot: 25 June. This was done to corroborate the figures from the London School of Hygiene and Tropical Medicine and referred to externally as the other data were not publicly available.
When unpublished figures are quoted in the public domain, we expect that this information is shared with the media and the public in a way that promotes transparency and clarity. There are lessons to be learnt in this case, with different data sources being quoted to the media and to us. We expect that any figures used are appropriately sourced, explained and available in the public domain.
Furthermore, it is important to recognise that a comparison of COVID-19 prevalence rates is not straightforward. If it is to be undertaken, the results and the uncertainties should be communicated transparently. We do not think that the sources above allow for a quantified and uncaveated comparison of the kind that was made. In future if such comparisons are made, we would expect to see sources made publicly available and a clear explanation of the limitations and associated uncertainty.
The Office for Statistics Regulation will continue to monitor Scottish Government’s use of statistics and data.
Yours sincerely
Ed Humpherson
Director General for Regulation
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