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Household Projections for Scotland, 2010-based

6. Definitions and limitations of the household projections

6.1 Definitions

6.1.1 The following definitions are used in this publication:

Figures in the tables are rounded to the nearest ten. Therefore, the totals shown may not be equal to the sum of all the constituent parts.

6.2 Limitations

6.2.1 These household projections have limitations. A projection is a calculation showing what happens if particular assumptions are made. The household projections are trend-based, and are not, therefore, policy-based forecasts of what the Government expects to happen. The do not take into account social and economic factors that may influence the formation of households including policies adopted by both central and local government as well as any imbalances between housing supply and demand. Local planning policies are often intended to modify past trends and development plans may demonstrate departures from the projections that seem better able to fit particular local circumstances.

Population projections

6.2.2 The household projections are based on the population projections and, as a result, assumptions used for the population projections, such as future migration, fertility and mortality, will have an effect on the household projections. Since smaller areas tend to be affected more by migration, which is hard to predict, projections for these areas tend to be less reliable than those for areas with large populations, and the further into the future the projections are taken, the less reliable they are likely to be.

The use of census-based trends in household formation patterns

6.2.3 The household projections use information on household type and age group from the 1991 and 2001 censuses, projected forward to the end of the projection period. This method assumes that past trends in household formation will continue, but this may not necessarily be the case. The overall number of households is updated every year, but no information is incorporated on changes in household types between censuses.

6.2.4 With the assistance of the Household Analysis Review Group, National Records of Scotland (NRS) has been investigating ways to refine the household projection methodology. Recent work has investigated a methodology that takes into account recent information on household formation. Incorporating information on recent trends in the proportions of households of each household type, using data from the Scottish Household Survey, has been trialled. We have chosen, however, not to use this methodology, as it introduces an additional source of variability without producing much improvement in the projections. A description of the trial methodology, along with results and analysis can be found in 'HARG 2012 (5)'.

6.2.5 NRS has also investigated the use of alternative headship rate projections (HARG 2011 (6)). As a result, headship rate variants are presented in this publication for the first time. The headship rate variant, like the migration variants of the population projections, gives an indication of how the assumptions made regarding future trends in headship rate affect the household projections.

Relationship to other projections

6.2.6 These projections apply a single methodology across all local authorities. Individual authorities may have a wider range of local information, based for example on local population or household surveys, on which to compile local projections. The supporting material on the NRS website should assist in providing an understanding of the basis of our projections. We are happy to provide additional supporting or background material which users would find useful in assessing and using the projections, where possible. Please contact us at [email protected]

 

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