Short-term migrants 'largely account' for immigration statistics gap
Migrants coming to Britain for short periods "largely account" for a gap in statistics which has fuelled claims that immigration from the EU may have been underestimated, an official report has concluded.
Rising numbers of people who stay in the country for between a month and a year were identified as the main factor behind differences between measures of long-term international migration and National Insurance (NI) numbers given to EU nationals.
The highly anticipated Office for National Statistics (ONS) report follows months of debate over large discrepancies between the two and questions over whether the headline figures capture the full scale of the inflow to the UK from the bloc ahead of next month's referendum.
In the year to September, just under 655,000 NI numbers - which are needed to work in the UK - were registered to EU citizens. Over the same period, the main immigration figures indicate 257,000 people arrived from the bloc.
The report said: "Short-term migration to the UK largely accounts for the recent differences between the number of long-term migrants ... and the number of National Insurance number registrations for EU citizens."
Short-term migrants are those who arrive for employment, study or other work purposes for between one and 12 months. L ong-term immigration figures only count those intending to stay in the country for at least a year.
Statisticians said their research showed many people who register for an NI number stay for less than a year.
Glen Watson, of the ONS, said it is confident the International Passenger Survey - based on hundreds of thousands of interviews of passengers entering or leaving the UK by air, sea and tunnel routes - " remains the best available way of measuring long-term migration to the UK".
He said NI number registrations are "not a good indicator" of long-term migration but do "provide a valuable source of information to highlight emerging trends", adding: "The number of short-term migrants coming to the UK to work or study has been rising recently, but you need to consider the short-term migrants leaving these shores as well to get the full picture."
The statistics show short-term migration by EU citizens is on the rise. It was estimated to be 251,000 in the year ending June 2014 - the highest number since the year ending June 2008, 5% up on 2013 and 35% up on 2012.
When short-term and long-term data are added together, there is a "much closer parallel" between the two measures, according to the report.
Long-term migration to the UK by EU citizens in the year ending June 2014 was 223,000, and when combined with short-term migration this gives a total of 474,000. This compares with 421,000 NI registrations.
In five years to June 2015, long-term migration by EU nationals was 915,000. When short-term migration is included the number is just under two million, while there were 1.8 million NI allocations.
The paper also provided the first indications of the proportion of NI numbers which are active on tax and benefits systems, following a clamour for the data to be released.
Up to 50% of citizens from eight Eastern European countries including Poland and the Czech Republic which joined the EU in 2004 have NI registrations that are active for less than a year, analysis showed. Almost two-thirds (61%) of Bulgarians and Romanians have NI numbers that are active for less than 12 months.
The ONS said this supports evidence that the gap between NI activity and long-term migration is likely to "largely be accounted for by short-term migration".
Figures released separately by the Government showed recently arrived migrants from Europe paid £2.54 billion more in tax than they received in tax credits or child benefit in 2013/14.
Migration Watch UK recently published analysis claiming EU migration may have been under-counted by up to 50,000 a year.
Alp Mehmet, of the campaign group, said: "What matters is the increase in the European-born population in Britain, which is not consistent with the immigration figures. This ONS report has not addressed that question."
Dr Carlos Vargas-Silva, of the Migration Observatory at the University of Oxford, said long-term migration estimates "fail to capture a range of potentially important changes in migration trends".
He added: "To provide a more complete picture we would need to monitor a range of indicators that include short-term migration flows."
Brexit-backer Boris Johnson said: "What it shows is that large numbers of people are coming, they are getting NI numbers, they are availing themselves of services which are under huge pressure at the moment."
The Government said the report is a "clear endorsement" of the validity of migration figures.
A spokesman said: "Despite recent questions about the figures, the ONS have now put this issue beyond doubt."
Short-term migrants have never been included in the long-term migration statistics, which are governed by UN definitions, he said, adding: "It would be completely wrong for anyone to try to distort or misrepresent these figures any further following the independent ONS's conclusions."
Jonathan Portes, of the National Institute of Economic and Social Research, said data suggested to him that there was a "degree of undercounting of long-term migration from EU member states".
He added: "I note ONS disagree with this view, and I respect their independent professional view. There are no clear 'right answers' here."