The Results of the "Special Case Scenarios"

1.  The results of the "special case scenarios" are presented in this section though they are based on less realistic assumptions and are mostly for reference purposes, though it can be argued that the zero migration (natural change only) variant could be realistic for Scotland as it falls between the high and low migration assumptions of the standard variants. Figure 9 compares the "special case scenarios" with the principal projection and shows that only under the replacement fertility scenario does Scotland’s population increase. The replacement fertility scenario assumes that the Total Fertility Rate (TFR) is just below 2.1. Currently Scotland’s TFR is 1.6 so the chances of this changing to replacement levels appear to be very slim.

2.  Figure 10 shows that, even under these less realistic scenarios, Scotland’s average age is projected to increase from 40.1 years, ranging from 41.6 years under the stationary projection to 45.8 years under the zero migration (natural change only) projection.

3.  The extent to which the population is not stationary under the stationary projection (i.e. the population does not have an unchanging size and structure) reflects the inherent "population momentum" resulting from the existing population age structure. It takes time for the population to reach stationary conditions i.e. unchanging size and structure.

4.  The dependency ratio, the number of people aged under 16 and of state pension age per thousand people of working age, is shown in Figure 11. It is projected to increase from 599 to between 645 under the no mortality improvement projection and no change projection to 753 under the replacement fertility projection.

5.  Unsurprisingly, the replacement fertility scenario causes the dependency ratio to rise because of more children being born. It is also interesting to note that the dependency ratio under the zero migration (natural change only) variant is very similar to the principal projection, showing that the assumption for migration in the principal projection has relatively little effect on long-term dependency ratios.

6.  In summary, the "special case scenarios" are based on less realistic assumptions. The replacement fertility scenario illustrates that with a fertility rate of around 2.1, Scotland’s population would increase in size and the ageing of the population would be slower than under the principal projection, though the dependency ratio would increase due to more children being born.

7.  The constant fertility projection produces very similar results to the principal projection in that the population is projected to reduce in the long-term, with a reduction in the dependency ratio as more people die off after 2020.

8.  The zero migration (natural change only) variant is of most interest as it is probably the only "special case scenario" that could be considered to be realistic for Scotland. That is, its assumption of zero migration falls between the high and low migration assumptions of the standard variants.  The effects of migration on population growth are explored further in Section 5.