Dear Mr Macdonald
Thank you for your letter of 3 July about the use of figures in a press release of 10 June by Public Health Scotland (PHS) concerning the impact of the first year of the Scottish Government’s policy on minimum unit pricing for alcohol. You were concerned that the data used in the press release misdirected subsequent media coverage of the research.
Having looked at the concerns in detail, we concluded that the main findings of the research (a net decrease in Scotland of between 4 and 5% in sales per adult over the first year of the policy) are dependent on the difference in movements in alcohol offsales in Scotland (a decline in sales of 2.6%) compared with England and Wales (an increase in sales of 2.3%). The researchers have controlled for different effects including using England and Wales as a geographical control. The results of using the geographical control and other controls such as household income gives slightly different results depending on which controls are applied, hence the range of the estimated decline in offsales of between 4 and 5% over the period. The figures in the press release are consistent with these findings.
The research has effectively reported an estimated change but has not reported the observed year-on-year change. There are areas where there could have been a clearer presentation in the press statement, particularly that the research reports an estimated effect of the policy change. The PHS statisticians we were told had no intention to mislead in the press statement, they were trying to keep the messages straight-forward.
It would have been helpful in the press statement to refer to the observed year-on-year decline in offsales as was apparently referred to in the Good Morning Scotland radio interview with the PHS investigator that you refer to. Also, there could have been a better explanation about the limitations in the statistics, and PHS might have included some indication of the range of the plausible reductions in offsales (-5.3% to -3.0%). PHS might also have provided some useful lines in the press release to help the media to interpret and quote the figures appropriately. Such explanations protect the integrity of the findings and support users of these numbers in drawing the correct conclusions to inform the decisions they make.
As you point out PHS is a new agency and through our engagement we have seen that its staff understand the importance of maintaining the standards required of the Code of Practice for Statistics. PHS is building on the strong pedigree of ISD Scotland, one of its component parts, and its statistics officials are working with staff across PHS to instil a culture which looks to draw heavily on the principles of the Code of Practice for Statistics and associated guidance.
The Office for Statistics Regulation will continue to work with PHS to ensure that support is provided as it develops its practices and will support them in applying the principles of the Code of Practice.
I am copying this letter to Scott Heald, Head of Profession for Statistics at Public Health Scotland, and Roger Halliday, Chief Statistician and Joint Head of Covid Modelling and Analysis Team at Scottish Government.
Yours sincerely
Ed Humpherson
Director General