New figures out yesterday from the Office for National Statistics (ONS) suggest that net migration – that’s the number of people coming to the UK minus those leaving – has fallen by a fifth since last year.

But the most striking revelation from yesterday’s publication is that net migration was a lot higher in 2022 and 2023 than the ONS originally thought.

The latest stats for this year are likely to be revised upward as more data comes in too. So can we actually be confident that net migration has fallen at all?

FactCheck takes a look.

Changing estimates

Yesterday, the ONS said it estimates there was net migration of 728,000 in the past year – that’s the 12 months up to June 2024.

And it says this is a drop compared to the previous year, to June 2023 – when they estimate it was 906,000.

But that 2023 figure has already been revised twice.

When the ONS initially estimated net migration for that year in November 2023, it gave a figure of 672,000. Then in May this year, it said that the number should actually be 740,000.

Now it’s revised the number again, up to 906,000. That’s nearly a quarter of a million more than the initial estimate from this time last year.

The ONS’ initial release had underestimated immigration to the UK, while also overestimating emigration.

And the ONS did something similar for the year before that – the 12 months up to June 2022 – ultimately revising its estimate up by around 130,000.

So over those two years combined, the ONS’ initial estimates of net migration actually fell short by 364,000 people. That’s a huge number.

But why did the figures change so much? And given the scale of previous revisions, do we have any reason to trust this year’s estimate?

Lacking information

The ONS says that it revises its estimates as it gets more complete data.

As an example, it says that it was previously missing some people arriving on the Ukraine schemes, and that correcting this omission added 43,000 people to its estimate for last year.

It also says that when someone arrives in the country, it doesn’t have all the travel information it needs to decide if that person will stay long enough to be considered a migrant – so it has to make assumptions based on the past behaviour of similar people.

So, with all these caveats, is this year’s estimate reliable at all?

The ONS said that its net migration figures are “official statistics in development”, and that it expects this year’s estimate to be more “resilient” to future changes.

It says it previously had to rely on survey data to estimate net migration, but it now has access to more reliable administrative data – for example, visa data from the Home Office.

And it says that visa data shows specific downwards trends, for example, fewer students bringing family members with them to the UK. Coupled with data showing rising emigration – the number of people moving away from the UK – it says all signs point to a fall in net migration.

But despite all this, the exact estimate will still be revised – so in the end, that headline figure of a 20 per cent drop is very likely to be revised too.

(Image credit: Dinendra Haria/LNP/Shutterstock)