Should we be using NI numbers to measure immigration?published at 16:15 Greenwich Mean Time 25 February 2016
By Beth Sagar-Fenton
Reality Check
An email arrives from UKIP. Nigel Farage is wondering why, as Jonathan Portes has been pointing out today, external, gross migration to the UK from the EU was 260,000 in the year to September, but during the same period, 650,000 EU nationals registered for National Insurance numbers.
"They are pulling the wool over our eyes," Mr Farage says.
"NiNos (National Insurance numbers) are a simple and clear reflection of the real numbers of people in this country, as without them you can neither legally work, nor claim benefits."
There is no question that the immigration figures, which are based on a survey taken at ports and airports, are imprecise, with the ONS 95% confident that the net migration figure is within plus or minus 37,000 of the true figure.
But using National Insurance numbers also presents problems. In particular, everyone who wants to work in the UK must have a National Insurance number, even if they're only working in the country for a few weeks, whereas the long-term migration figures only count people planning to stay for a year or more.
Also, the migration stats include many people who are not planning to work or claim benefits, such as children or non-working partners. People applying for a National Insurance number could have arrived at any time, not necessarily in the year or quarter in question.
So the difference between the two figures is striking, but National Insurance numbers are not a better figure to use than the migration figures.