Variant population projections are more important than ever

PGRG Blog #5, November 2017

Nik Lomax
University of Leeds

This week, the Office for National Statistics (ONS) released six extra variants for the 2016 based National Population Projections (NPPs).  The intention of these variants is to provide results from ‘particular, but not necessarily realistic’ assumptions which can be compared alongside the projection variants available as part of the main  2016 NPP release. The impact of these various assumptions can be assessed using the excellent visualisation tools produced by ONS which reveal that of all the 18 main or extra variants, the population of the UK in 2041 is projected to range between 77 million under the ‘high population’ scenario (which assumes high fertility, high life expectancy and high migration) and 67.3 million under the ‘zero net migration’ scenario (which assumes international immigration and emigration balance one another). The principal projection is for a UK population of 72.9 million in 2041. Clearly the difference between these scenarios is substantial, and the ONS offer a commentary on the variants alongside the visualisations and data, so I won’t duplicate that here.

The projection variants which caught my eye are those where the assumptions about future EU migration from mid-2019 onwards are varied. ONS are clear that these three variants are not classed as National Statistics in the way that other variants are, and that their ‘projections do not attempt to predict the impact of the UK leaving the EU’. However, the projections to 2041 under three scenarios vary considerably which provides a useful guide to how sensitive the UK population is to EU migration. 0% future EU migration beyond 2019 produces a projection of 70.1 million people, 50% future EU migration an estimate of 71.5 million and 150% future EU migration a projection of 74.3 million, so a difference of 4.2 million over a 25 year period between the highest and lowest projections.

These differences under the three EU migration scenarios demonstrate the need for further research on the impact that future policy or economic conditions will have on the size and composition of the UK’s population. This is especially pressing, given current uncertainty around future policy on migration and the economic conditions the UK will face after the UK leaves the EU.

Research in to these different migration scenarios is something we are working on as part of the NewETHPOP project, where we project the size and composition of the UK’s ethnic group populations.  By altering the international migration assumptions we can produce a range of possible scenarios of future population, by age, sex and ethnicity. We have already reported the difference between a baseline no migration scenario (unrealistic, but useful to see what the impact of that component is) and a no-Brexit scenario. The results for the size of the population are not unexpected, with steady growth under the no-Brexit scenario and population decline under the no migration scenario. The latter is consistent with the ONS no migration scenario. Most interesting however is that we conclude under both scenarios the UK population will continue to age and will also continue to become more diverse in its ethnic composition. This is because of the demographic momentum of some ethnic minority groups, and the relatively older age structure of the White British population. Of course the most likely reality in terms of population size and composition will be somewhere between our no migration and no Brexit scenarios, and we are currently working on these variants so that they can help inform policy debate.

 

Nik Lomax
University of Leeds


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