How much has immigration contributed to population growth in the UK?

Immigration is a highly politicised topic in the UK, having come to the forefront of the political debate over the last few years. In this post, I do not take a position in the debate over immigration; nor do I even analyze any of the relevant arguments. Rather, I simply consider the extent to which recent immigration has contributed to population growth.

It is widely believed, rightly or wrongly, that immigration was too high under the previous Labour government. And this is true not only among Conservatives and UKIP supporters, but among Labour supporters and Liberal Democrats as well. A 2013 YouGov poll found that 74% of Labour supporters and 59% of Liberal Democrats, along with 92% of Conservatives and 98% of UKIP supporters, thought that the last Labour government admitted too many immigrants. And according to a 2012 YouGov poll, among individuals who voted Labour in 1997, 67% of those who also voted Labour in 2010 want zero net migration, while 78% of those who voted for another party in 2010 want zero net migration.

The first chart (below) plots net migration in the UK between 1970 and 2012, using data from the ONS. Between 1970 and the early 1980s, net migration was low and negative. It turned low and positive during the mid-1980s. Beginning in approximately 1997, it increased markedly to about 150-200 thousand net migrants per year, where it remained throughout the 2000s.

The second chart (below) plots cumulative change in population between 1997 and 2012. The continuous line describes the change that was actually observed, while the dashed line describes the change that would have been observed if net migration had been zero. By 2012, the actual population was 5.06 million larger than it had been in 1997. Under zero net migration, the population in 2012 would have been 2.19 million larger than it had been in 1997. Therefore, approximately 57% of the population growth that took place between 1997 and 2012 may be attributable to immigration. Overall, the UK population might have been 5% smaller by 2012 under zero net migration. Note that this analysis only considers the direct effect of immigration on population growth. It does not account for differential fertility between immigrants and natives.