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The Progressive Policy Think Tank

Flawed migration statistics fuelling poor policy, says IPPR

New ONS analysis of exit checks and visas shows fundamental problems with quality of migration data

Marley Morris, IPPR Senior Research Fellow, commenting on today’s migration data from the ONS, said:

“New analysis today from the ONS places serious doubt on its migration estimates.

“Comparisons of ONS migration data and statistics on visas and exit checks suggest that it has underestimated non-EU emigration, particularly in the study category. In our view, the new analysis suggests it has overestimated net non-EU migration.

“Given the underlying problems in the data, it’s no longer sustainable that the government centres its strategy on bringing down net migration to the tens of thousands.

“Currently our system is designed to encourage migrants who come to the UK to leave after a short period, irrespective of their skills. We need a new approach to migration that meets our economic needs.

“In particular, we currently encourage international students to leave the UK after their studies, on the basis of flawed information that many overstay their visas. We need to do the opposite: by introducing a post-study work visa we can encourage those students we have skilled up at our universities to stay and contribute to the UK economy.”

Today’s ONS analysis finds significant discrepancies between measures of migration drawn from the International Passenger Survey (IPS) and administrative data from visas and exit checks. The IPS, a sample survey conducted at UK ports and airports, is the basis of routine ONS migration estimates used by government to formulate policy.

The new analysis follows last year’s ONS discovery, in its review of student migration, that the International Passenger Survey appeared to have overestimated the contribution of non-EU international students to net migration.

IPPR’s interpretation of the ONS’s new analysis is that this has led to an overestimate in the net migration of non-EU citizens.

There is little evidence, however, to question the overall net migration estimates, as any inaccuracies in the non-EU migration figures could be compensated by inaccuracies in the EU migration and British migration figures.

The ONS also today published its quarterly migration statistics. These indicate that in the year ending December 2017 total long-term net migration to the UK was 282,000, compared to 249,000 in the year ending December 2016. This change is not statistically significant. 

It should be noted that these migration figures are estimates only and are subject to both sampling and non-sampling error.



David Wastell / 07921 403651

Florri Burton, / 020 7470 6154

Marley Morris, IPPR Senior Research Fellow, is available for interview


Read IPPR’s latest report on migration ‘An immigration strategy for the UK: Six proposals to manage migration for economic success’ here: 

Read Marley Morris’ blog on migration statistics, published ahead of the latest analysis:

Read IPPR’s report comparing migration data on international students ‘Destination Education’ here: 

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