National Records of Scotland

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The Results of the "Single Component" and Standard "Combination" Variants

The Results of the "Single Component" and Standard "Combination" Variants

1.  The results of the range of "single component" and standard "combination" variant projections are illustrated in Figure 1.  The future size of Scotland’s population is uncertain.  Under the high and low assumptions of future fertility, life expectancy and migration, the total population of Scotland at 2031 would vary between 5.3 and 4.8 million.  But under "extreme" combinations of these assumptions, the population could be as high as 5.6 million or as low as 4.6 million.  Figure 1 also shows that future population growth is possible under the "high" population variant, the "young" variant, the high migration variant, the high fertility variant, the high life expectancy variant and the low dependency variant to 2031. 

2.  However, while population decline is not inevitable, Figure 2 demonstrates that population ageing will occur under any plausible set of assumptions.  The proportion of Scotland’s population aged 65 and over is likely to increase from 16 per cent now to between 25 per cent and 27 per cent by 2031.  Even under the "extreme young" combination of high fertility, high net migration and low life expectancy assumptions, the proportion would rise to 23 per cent; and the corresponding "extreme old" combination would produce a rise to 29 per cent.

3.  The inevitability of population ageing is a consequence of the current age structure of the population.  This, in turn, is a result of changes in the past numbers of births.  Thus, during the first half of this century, the number of elderly people will rise as the relatively large cohorts born after the Second World War and during the 1960s baby boom replace at older ages the much smaller cohorts born previously.  Also, the smaller cohorts born since the mid-1970s will replace the baby boomers.

4.  As well as looking at the differences in the projected level of Scotland’s population and the proportion aged 65 and over, it is also useful to look at demographic indicators which give a suggestion of the consequences of the different assumptions on Scotland’s population.  This section looks at different groups in the population, the average and median age [Footnote 1] and also dependency ratios [Footnote 2] under the "single component" and standard "combination" variants.

5.  The effect of the different assumptions used in the variant projections on the size of the population aged under 16 is shown in Figure 3

6.  All the projections show the number people aged under 16 falling by 2031 except for the "young" combination and the "high" population variant.  The biggest falls are projected under the "old" variant and the "low" population variant.

7.  The number of people of working age is projected to decrease over time for nearly all the projections (as illustrated by Figure 4), especially after 2020 when the large birth cohorts from after the Second World War and the 1960s move into older ages and the birth cohorts of those turning 16, fewer in number, start to age.

8.  The number of people of working age would increase slightly by 2031 under the "high" population variant, and the "young" combination variant.  Under the high migration variant the working age population decreases slightly compared with the 2004 level.

9.  In contrast, the population of state pension age is projected to increase by 2031 under all the projections (as shown in Figure 5)  especially after 2020 when the baby boomers reach state pension age and the change in women’s state pension age to 65 is complete.

10.  Under the principal projection, the average age of Scotland’s population is projected to increase from around 40 years in 2004 to 45.2 years by 2031, as illustrated by Figure 6.  Similarly, the median age is projected to increase from 39.8 years in 2004 to 45.5 years by 2031.

11.  The average age increases under all the projections as Figure 7 shows.  Reinforcing the point that while there is uncertainty about the future level of Scotland’s population, the ageing of the population seems inevitable.

12.  The average age is projected to be highest under the "low" population variant and lowest under the "high" population variant.  Also, the high fertility variant projects a slightly lower average age than the high migration variant by 2031.

13.  Another useful indicator of the population structure is the dependency ratio: the number of people aged under 16 and of state pension age per thousand people of working age.  It should be emphasised, however, that demographically defined dependency ratios, whatever age boundaries are used, take no account of workforce participation rates and therefore do not represent real levels of economic dependence.  In reality, full-time education ends, and retirement starts, at a range of ages. 

14.  Figure 8 shows the dependency ratios under the different projections.  The combination of a declining population and a sharply rising elderly population will cause the dependency ratio to rise.  Under all the variants, the dependency ratio is projected to remain at around 550 to 620 dependents per 1,000 people of working age until 2021.  It is only after 2021, and the completion of the change to women’s state pension age (and the baby boomers reaching state pension age) that the dependency ratio rises: ranging from 685 under the low fertility variant to 733 under the low migration variant.  Even under the "extreme" combination assumptions of the "low dependency ratio" variant the dependency ratio will still rise to 648.


1.  Median age: 50 per cent of the population is below this age and 50 per cent is above this age – the middle age of the population.

2.  Dependency ratios show the relationship between the working age population and the two main dependent groups – children aged under 16 and people of state pension age.

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