Census 2012: population rise due to dodgy data

ONS says 45% of increase due to failings in the 2001 figures, the rest is attributed to an underestimation of net migration

Are we filing up too fast? On census day, 27 March last year, England and Wales contained 56.1 million people – up by 3.7 million, a shade over 7% in a decade. This is the biggest increase since the census began in 1801, with half a million more than the statisticians expected.

In British political life there are few subjects as touchy as immigration and any undercounting will lead to suspicions that foreigners are silently slipping into the country. The truth appears more prosaic. The Office for National Statistics says 209,000 (45%) of the unexpected difference is because of failings in the 2001 census.

Another 267,000, representing 55% of the population increase, was “attributed to an underestimation of net international migration over the decade”. The census admits that it missed young people aged 10 to 19 from abroad and women aged 25 to 44.

This is important as immigrants have more children. The ONS’s latest figures show that although British-born mothers are more fertile than before, they still have fewer babies on average (1.88) than foreign-born mothers (2.45), who account for a quarter of all births.

It is true that many migrants end up in London, where the population density is an uncomfortable 5,200 people per square kilometre – compared with England’s national figure of 371. But as Matt Cavanagh of the Institute of Public Policy Research (IPPR) points out, that is because the capital is the nation’s economic powerhouse – sucking in people and investment.

Underlying the debate is the fact that calculating immigration relies on using the notoriously unreliable international passenger survey, which is too small and does not sample randomly. The result is dodgy data. A little less than 15% of the total amount can be directly attributed to people who were coming to stay but decide to leave. A fifth is to do with travel across the Irish Sea.

Two-thirds of the missing 267,000 is down to the survey “underestimating immigration or overestimating emigration”. How many people leave the country is as important as how many enter, especially last year, when about 30,000 UK citizens emigrated – the lowest for almost a decade. The Migration Observatory at the University of Oxford points out that there are 2.23 million EU migrants in Britain but 1.42 million Britons living on the continent.

Scott Blinder of the Migration Observatory team said the government’s proposed capping of immigration to “tens of thousands” would be ineffective if errors this large were allowed to persist, adding that the government’s e-Borders electronic system for counting in people and counting them out was two years from producing data.

There’s no doubt immigration is important. Once Scotland and Northern Ireland are added in, Blinder says Britain’s population will top 63 million by 2011. It is estimated that net migration accounted for more than half of the 3.7 million increase in the population of England and Wales in the last decade.

But Migration Observatory says the idea that governments could arbitrarily define a limit to the nation’s population – the coalition thinks 70 million might be appropriate for the UK – was not rooted in “credible evidence”.

There is an economic cost to the country of limiting immigration. Last week, the Office for Budget Responsibility’s central assumption was that net inward migration will fall to about 140,000 a year – it is presently about 250,000 – and will remain there over the next five decades. That would require spending cuts and tax rises of £17bn to bring down the national debt to 40% of GDP by 2062. If the current rate of immigration is allowed to continue that falls to £4.6bn.

Unless the government straps rocket boosters to the economy, the choice in the future might be boiled down to importing growth or cutting public spending.


guardian.co.uk © 2012 Guardian News and Media Limited or its affiliated companies. All rights reserved. | Use of this content is subject to our Terms & Conditions | More Feeds