Variant projections provide a broad indication of the sensitivity of the household projections to the demographic assumptions that are used to produce them. The principal household projections are based on the principal population projections produced by GROS which use assumptions about fertility, mortality and migration which are thought most likely to occur over the next 25 years. Variant projections are based on alternative assumptions of future fertility, mortality and migration. For the 2006-based population projections, GROS produced a high migration variant projection at sub-national level for the first time.
The high migration variant projection uses the same assumptions about fertility and mortality as the principal projection but assumes higher levels of net in-migration to Scotland2. The migration assumptions by council area can be found in Annex D and Annex E of the 2006-based Population Projections for Scottish Areas (http://www.nrscotland.gov.uk/statistics-and-data/statistics/statistics-by-theme/population/population-projections/sub-national-population-projections/archive/2006-based)
The high migration variant household projection is calculated by replacing the principal population projections with the high migration population projections and keeping all other inputs (communal establishment rates, headship rates, household estimates) unchanged.
The high migration variant projection shows the number of households in Scotland increasing from 2.29 million in 2006 to 2.85 million in 2031. This compares to 2.73 million households in 2031 under the principal projection. Figure 8 illustrates this along with the projected increase in population for the principal and variant projections.
The average annual increase in the number of households is 22,200 under the high migration variant projection compared to 17,600 under the principal projection.
Table 18 shows the projected number of households for each local authority area under both the principal and high migration variant for selected years as well as the percentage difference between the projections in 2031. The high migration variant has the biggest impact on Aberdeen City (where the number of households is 10 per cent higher than under the principal projection) and Edinburgh (8 per cent higher). The population in these areas has increased the most under the high migration variant projection since they are areas that gain the most migrants from outwith Scotland.
Figure 9 compares the percentage change in households from 2006 to 2031 under the principal and high migration variant projections. The impact of the high migration variant on different local authority areas can again be seen here, with Aberdeen City and Edinburgh City having the biggest difference between the two sets of projections.
Figure 8: Principal and high migration variant, 2006-based population and household projections for Scotland.
Figure 9: Percentage change in households 2006 – 2031, using the principal and high migration variant projections, by local authority area
