Ed Humpherson, Director General for Regulation, Office for Statistics Regulation writes to Ken Roy, Head of Profession for Statistics, Department for Environment, Food and Rural Affairs (Defra).
A concern was raised with us about the use of a statistic in a Defra press release from 17 April.We were asked to investigate the source and credibility of the statistic in the statement “… a recent study showing 8.5 billion plastic straws are thrown away each year in the UK”.
We understand that the 8.5bn figure comes from the report ‘Leverage Points for Reducing Single-use Plastics – Background Research’ by Eunomia, an independent consultancy group. The figure is an estimate of the number of single-use straws consumed on the fast food market in the UK per year. The figure was derived using an estimate of the number of single-use straws consumed by a fast food chain in the UK per day, together with data on the number of fast food chains in the UK.
It is disappointing that the source of the 8.5bn figure was not mentioned in the press release. It is important to always include a prominent link to the source of a statistic in a press release, regardless of whether that source is a government official statistics output or an independent report. Being open and transparent about sources promotes public confidence in Defra’s use of statistics.
We are satisfied that Defra took appropriate steps to check the credibility of the estimate. Your team told us that statisticians in the Waste Statistics team had sight of the briefing before it went out. The team verified the origin of the figure and checked the figure with another organisation that is doing commissioned research for Defra on single-use plastics. The figure was deemed to be sufficiently credible for use in policy and communications briefings and was endorsed by the Defra Head of Waste and Resourcing. This process seems sensible and we welcome that the teams considered the context in which the estimate was used.
The 8.5bn figure is the only published estimate available of the number of plastic straws used in the UK. We recognise that, in the absence of a range of estimates, Defra chose to use this estimate. However, Defra could have been more cautious in its wording in the press statement. The press release talks about a “recent study showing 8.5 billion plastic straws are thrown away each year in the UK”. As highlighted above, the study combines several sources of data to derive an estimate of the number of single-use straws consumed on the fast food market in the UK per year. Therefore, it would have been more accurate to talk about a “study estimating”. This point does not materially affect the story, but it would have aided interpretation of the figure and helped readers understand that there is a degree of uncertainty around the figure.