Impact of immigration on UK population growth

Impact of immigration on UK population growth

23 August, 2018


1. The population of the UK rose by a total of 6.6 million between 2001 and 2016. The latest research shows that just over 80% of this increase was due to immigration - that is to say new immigrants and their UK-born children.


2. With respect to estimating the impact of immigration on population growth, the ONS annual mid-year population estimates state the proportion of annual growth due to net migration and to natural increase (that is, the excess of births over deaths). However, they do not go further and attempt to attribute a proportion of the natural increase to immigrants.

3. The ONS also make an estimate of the impact of immigration and natural growth on future population growth in their biennial population projections. The latest one is based on 2016. As it happens, the ONS high migration assumption matches closely the average annual net inflow over the past ten years (about 250,000 per year). Projecting the impact of immigration forward from the year 2016 to 2041 gives a figure of about 82% of the projected population increase of nearly ten million between 2016 and 2041 being due to immigration, both directly and indirectly (that is, from the natural increase of post-2016 immigrants). This result, however, is dependent on the assumptions made rather than a calculation of what has actually happened.

4. To estimate the latter, Migration Watch UK has expanded the ONS calculation of the immigration contribution to past population growth to take into account the contribution to annual population growth made by the annual births of children of immigrants. We have also introduced an adjustment to take into account the annual deaths of immigrants in the UK and the annual deaths of the children of immigrants who were born in the UK.


5. High immigration since the early years of this century has taken UK population growth to record levels (see figure 1 below).

Figure 1: UK population 1901-2017. Source of data: ONS.

6. The direct contribution of immigration is relatively easy to calculate – it is the total of net migration each year, minus the total number of immigrants who died in the UK in that year.

7. However, there is also a second component, namely children born each year to immigrant parents after their arrival in the UK. From these should be subtracted the number of deaths in the UK each year to the children who were born in the UK to immigrant parents. This is the indirect contribution of immigration. (Countries with population registers, such as The Netherlands, can determine exactly the size of this immigrant-descended population and hence the population of ‘immigrant background’ as it is termed.)

8. From the 1970s until the mid-1990s, about 12% of births in England and Wales each year were to mothers born outside the UK (irrespective of citizenship), about 7% in Scotland and fewer in Northern Ireland. Since the late 1990s that proportion has more than doubled as a result of the great surge in immigration following policy changes after 1997 when Labour returned to power. It continues to increase each year. In 2016, 29% of births in England and Wales were to mothers born abroad and 28% were to foreign-born fathers (country of birth of fathers is not always recorded). In total, 34% of births had at least one parent born abroad. Births in England and Wales where both parents were UK born correspondingly declined from 85% in 1974 to 66% in 2016.

Figure 2: Percentage of births to immigrant parents. England and Wales 1974 – 2016.

Note: this data include people of British origin (and citizenship) born overseas.

9. Many children with immigrant parentage had one parent born in the UK and the other born abroad. Those children should only be regarded as making a 50% contribution to UK population growth. Where both parents were born abroad, all children should be added to the total.

10. It is also necessary to account for deaths of the children of immigrants each year (not the deaths of the immigrants themselves, already incorporated). The methodology is explained in Annex A and results in an estimate of approximately 20,000 a year in recent years.

11. The results of these calculations are tabulated in Table 1 below. It will be seen that the percentage of our population increase attributable to the direct and indirect effects of immigration has fluctuated between 71% and 91% between the years 2001 and 2016 with an average of 82%. In view of the indirect estimation of the mortality of the UK-born children of immigrants, this component should be regarded as approximate although its size is likely to be small compared with other components of the calculation.

Table 1: Annual components of population change UK 2001- 2016.

Calendar YearNet migration Deaths of migrantsNet migration discounted by deaths of migrantsBirths to migrantsDeaths of children of migrantsNatural increase of population with immigrant parentsDeaths not with immigrant parentsBirths not with immigrant parentsNatural increase not with immigrant parentsAnnual increaseActual increase. Net migration + total natural increasePercentage of UK annual population growth from migration, direct and indirect

12. The result is that the UK population increased by 6.6 million between 2001 and 2016 and migration (3.1 million) together with a natural increase of migrants (2.3 million) accounted for 5.4 million or 82% of that total. Figure 3 presents some of these data as a graph.

Figure 3: Population growth from migration & natural increase (thousands).

13. These calculations will include a relatively small number of people of British origin whose parents were living overseas when they were born (for example children of servicemen and women born in Germany) but the numbers are not significant.

14. The grandchildren and great grandchildren of immigrants have not been included in these calculations. Such data are unavailable for the UK. In any case most people would assume that such persons should be regarded as members of the indigenous population.

Annex A

Estimating the number of deaths of the children of immigrants

The procedure for estimating the number of deaths of the children of immigrants is complex and involves a degree of assumption and interpolation.

These deaths are not recorded as being of the children of immigrants. So no ‘off the shelf’ figures are available.

In brief, the estimation begins by generating successive populations of children born to immigrants using published data on births to immigrants for all available years and estimating for earlier years using census data and an estimate of the immigrant crude birth rate.

That produces a series of birth cohorts which are turned into a series of populations starting from 1911 through appropriate survival data. These populations produce the number of deaths that are needed, although only for the whole age-range from 2001 onwards. That, along with other factors, limits the scope of our estimation to the period from 2001 to the present.