Human behaviour, unreliable records: Why the UK keeps revising its migration data

In May last year, we learned that net migration to the UK (the number of people immigrating minus the number emigrating) had reached an unusually high level of 606,000 in 2022. Except it hadn’t – it was actually 745,000, we were told later in the year.

This spring, the 2022 figure was revised up again to 764,000. Third time lucky? No. Now the Office for National Statistics, or ONS, believes that net migration in 2022 was actually 872,000, 44% higher than the original estimate.

More recent figures have also been revised. While the ONS originally estimated the net migration figures for the year ending June 2023 at 740,000, this has now been revised to a record-high 906,000.

As a result, the drop from 906,000 to the latest figure of 728,000 in the year ending June 2024 is nearly 20%. But this too could still be revised in the future. Casual observers would be forgiven for being confused.

Difficulties in getting numbers right

Before the pandemic, migration statistics were produced from a survey of people passing through ports and airports. The figures were revised after an initial publication, but not very much – often by only one or two thousand. The problem was that they were wrong.

Or, as the ONS more politely put it, the survey in...

Read more