ISSUES
: Our Changing Population
Chapter 1: Population in the UK
11
The impact of migration on UK
population growth
Based on official population estimates and population projections, this briefing
examines the impact of migration on recent and future UK demographic trends.
Key points
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More than half (54%) of the
increase of the UK population
between 1991 and 2012 was
due to the direct contribution of
net migration.
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Differences in net migration
assumptions between the ‘low’
and the ‘high’ variant projections
produce a range of variation of
3.3 million in the projected size
of the UK population in 2037
(between 71.6 and 75.0 million).
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In the principal projection the
cumulative net inflow of post-
2012 migrants accounts for
43% of total population growth
until 2037. A further 17% of
projected population growth
is attributable to the additional
contribution of new migrants to
natural change (i.e. births and
deaths).
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The projected contribution of net
migration to population change
considerably differs across the
four UK constituent nations.
Without
net
immigration,
Scotland’s population would
stagnate over the next two
decades and decrease in the
longer term.
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Net migration assumptions
have been continually revised in
the projections released since
the mid-1990s, reflecting rising
levels of net migration and the
high uncertainty of migration
forecasting. The reduction in
assumed net migration levels
in the latest projections (relative
to the previous 2010-based
release) does not result in
significant slowdown of future
population growth because
of the concurrent projected
increase of fertility and life
expectancy.
Net migration
exceeded natural
change for a decade
Population estimates show that net
migration was a major component
of population growth over the past
two decades.
In particular, annual net migration
has substantially increased since
the beginning of the 1990s,
exceeding natural change as a
driver of UK demographic trends
in all years from mid-1998 to mid-
2011. However, natural change
has remained positive throughout
the last two decades and has also
continually increased from 2001
onwards, in particular due to a rise
in the number of births. As a result
of a significant drop of net migration
(by almost 100,000), 2011–12 was
the first year in more than a decade
when natural change contributed
more to the growth of the UK
population than net migration.
Overall, between mid-1991 and
mid-2012 net migration (resulting in
an addition of 3.4 million people to
the UK population) accounted for
just over half (54%) of UK population
growth.
However,
this
retrospective
analysis does not account for the
contribution of past migration to
natural change – mainly to births,
given that migrants are mostly
young, healthy individuals. The
number of births over a given
period is determined both by the
size and age structure of the female
population and by fertility rates (i.e.
the average number of children
per woman in each age group).
Migration impacts on both factors –
i.e. it affects the number of women
of childbearing age and, if migrant
women have different fertility
patterns, the total fertility rate of
the population as a whole. A recent
ONS report (Dormon 2014) using
the latest Census data for England
and Wales has shown that births
to foreign-born women made up
25.5% of all births in 2011, up from
16.4% one decade earlier (2001).
For a shorter period (2001–07) and
for the UK as a whole, Tromans
et al. (2009) estimated the overall
contribution of foreign-born women
to the increase in number of births
at 65%. However, this was mainly
due to the increase in the number of
foreign-born women of childbearing
age – total fertility rates of non-UK
born women remained constant
between 2001 and 2011 (2.21 in both
years), resulting in a decreasing gap
with the fertility levels of UK-born
women that increased from 1.56 to
1.84 over the same period (Dormon
2014). While these figures certainly
point to the significant indirect
contribution that immigration is
making to UK population trends, it
has to be noted that this analysis,
by referring to country of birth:
(a) considers a temporally broad
definition of the migrant population
(i.e. the overall impact on births of
in-migration over the past three
or more decades, not only the
contribution of those who moved
to the UK during the observed
period) and (b) does not single out
the effect of emigration (of both UK-
and foreign-born women) and of
immigration of UK-born women.
UK population
projected to grow to
71–75 million by 2037
The projected size of the UK
population in the period to 2037,
including high migration, low
migration, ‘balanced’ net migration
and zero net migration variants of
the 2012-based projections.
In the principal projection of net
migration at +165,000 per year,
the size of the UK population is
