Why uncertainty about immigration statistics is proving challenging for public understanding
The latest release of figures on net migration from the Office for National Statistics (ONS) received widespread coverage and even prompted a speech from the Prime Minister, as well as a range of comments by his political opponents. However, a crucial detail about the uncertainty of the figures was largely ignored. How helpful are such revisions to public understanding?
New figures published by the ONS on 28 November 2024 estimated that net migration to the UK in the year to June 2024 fell to 728,000. But if you read the full release, you can see that the actual figure probably ranges somewhere between 598,000 and 760,000. The ONS say they’re 95% certain about this range, but they add that their ‘uncertainty intervals should be interpreted with caution’.
Indeed, the release of these new figures should have served as a reminder about how uncertain they really are. As you can read in our explainer, the estimate for net migration in the year ending June 2023 was increased from 672,000 to 906,000.
Professor Brian Bell, Chair of the Migration Advisory Committee, told the Today programme that this increase was “surprising”, but should it have been? After all, the ONS clearly described the release as ‘official statistics in development’, and previously called them ‘experimental statistics’. As the ONS said in their release, they haven’t decided yet ‘whether the statistics are of sufficient quality and value to be published as official statistics, or whether further development is needed’.
It’s apparent that the ONS cautions about the data were not sufficiently heard, despite their efforts. They pre-released the figures to two representatives of PA Media ‘to facilitate well-informed debate and support better public understanding of the statistics’, but was this approach ever going to be sufficient for a release about a leading political issue?
We may well find ourselves re-visiting the same issue next May, when the next release of migration data is scheduled. More imminently, the government has committed to publish a White Paper ‘to reduce immigration’, presumably informed by the uncertain figures just published. There’s a real risk that policy changes and public opinion could be informed by inaccurate interpretation of figures that might be lacking sufficient quality.
Politicians, the press and the public need to be better informed about an issue of such significant interest. We commend the ONS for trying to develop statistics that meet this need, but until more reliable figures can be produced, it’s vital that ‘official statistics in development’ are better understood as such. We will be checking claims about the data - and raising concerns about its communication - to make sure the public is better informed, but until the data is more reliable there will always be limitations in what we can say.