Official estimates of migration to and from the UK have been wrong for several years, according to the Office for National Statistics (ONS) this morning.
As a result, those estimates have lost their quality mark from the UK Statistics Authority while work is done to improve the figures.
So what does all this mean? Here are five things to bear in mind.
1. Concerns about migration figures aren’t new – today brings new evidence of what’s gone wrong
Our main estimates of immigration come from a survey of passengers at the UK border. It distinguishes immigrants from visitors by asking people how long they intend to stay in the UK or be out of the country for, and eventually those become our main estimates of migration to and from the UK.
But as Professor Jonathan Portes of King’s College London pointed out last year, there’s a mystery: the figures we get from this survey haven’t been telling the same story as other sources of data on immigration.
Basically, there are apparently more EU citizens living in the UK than can be accounted for by the figures on EU immigration. And by contrast, there are fewer non-EU citizens living here than the non-EU immigration figures suggest (by a roughly similar amount).
While there are differences in what population and immigration figures measure (and how they go about measuring it), those alone don’t explain the whole mystery.
The bulk—though not all—of that mystery was explained today.
2. EU immigration to the UK has been underestimated
The ONS currently thinks EU net migration to the UK (the difference between the number who come and the number who leave) was about 35,000 a year higher than previously thought between 2009 and 2016. It cautions that this estimate may still change as it continues to investigate the figures.
For the 12 months ending March 2016, it estimates 207,000 more EU citizens immigrated to the UK than emigrated, whereas previously it thought that figure was 178,000. (The ONS hasn’t created new estimates for years more recently than 2016).
It says a big part of this is due to the fact that certain people who come to the UK don’t know what they’re going to do in the future, and this uncertainty means the figures we get about immigration—based on that survey of people’s intentions—are less reliable.
The ONS points out that people from EU countries, in particular the “EU8” countries from central Europe (Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Slovakia and Slovenia), are much more likely to be uncertain about their future intentions than other groups.
Crucially, we don’t know how accurate figures since 2016 are, because the ONS says there’s not enough evidence to re-adjust those yet.
3. Non-EU immigration to the UK has been overestimated
On the flipside, the ONS has revised down its figures for non-EU net migration by about 25,000 a year between 2012 and 2018. For the 12 months ending December 2018, it estimates that 214,000 more non-EU citizens immigrated to the UK than emigrated from it. Previously that figure was 232,000.
Again, uncertainty in people’s intentions is a key factor, and the ONS points out evidence that students in particular tend to be uncertain about where they will go after graduating. It says it’s likely that the number of students emigrating from the UK has been underestimated. Over half of non-EU immigrants to the UK say they come here to study.
4. Overall, the two changes roughly balance each other out
The ONS largely stands by its existing estimates for overall net migration—for now. In the 12 months ending March 2016, it says the overall effect of its adjustments so far makes net migration 1% higher than it previously thought.
We don’t know how accurate the total figures since 2016 are though, since the ONS has only adjusted the non-EU estimates for that time.
5. For now, we need to be wary of migration figures, and wait for more changes
As a result of today, migration figures will now be called “experimental statistics” rather than “National Statistics”. This basically means they’ve lost their quality mark, because the ONS can’t guarantee that the estimates are robust and reliable enough, and so they will now effectively have a caution flag attached while work continues to improve them.
Today isn’t the last time you’ll be reading about changes to migration figures.
The ONS has been doing work to adjust migration figures so they better reflect reality—and that’s why we have all these new numbers out today. But crucially, they haven’t been able to adjust everything, because the sources of data since 2016 aren’t clear on how the immigration figures might have been changing.
There’s still a key evidence gap in EU migration since the referendum, and “we cannot assume that EU migration post-referendum has necessarily been underestimated”, according to the Migration Observatory at the University of Oxford.