2.1 It is increasingly important to have high quality statistics on migration and the population, for policy development and for planning and providing public services. Population projections can be used to help with the planning of services in different geographical areas.
2.2 The primary purpose of sub-national projections is to provide estimates of the future population of areas in Scotland as a common framework for use in resource allocation and local planning in a number of different fields such as education and health. These projections are used as inputs to Grant Aided Expenditure (GAE) funding allocations and looking at the implications of an ageing population. They are also used for making comparisons between areas, as inputs to the National Records of Scotland (NRS) household projections, and as controls for small area population projections.
2.3 But population projections have limitations. A projection is a calculation showing what happens if particular assumptions are made. The sub-national population projections are trend-based. They are, therefore, not policy-based forecasts of what the government expects to happen. Many social and economic factors influence population change including policies adopted by both central and local government. The relationships between the various factors are complex and largely unknown. A principal projection and variant projections are given for each area in this publication, but all involve inherent uncertainty which is difficult to quantify.
2.4 The effect of the assumptions about future migration, fertility and mortality is often limited by the inertia in population change, the future population of an area is strongly influenced by the initial base population. As the process of change is cumulative, the reliability of projections decreases over time. Change affects some populations more rapidly and more seriously than others. Thus, projections for areas with small populations tend to be less reliable than those for areas with large populations, because the former are usually affected more by migration. Projections of the number of adults (particularly elderly people) are usually more reliable than those for children because of difficulties in projecting levels of fertility and parental migration. The size of the migration flows, and the uncertainty of future trends, mean that for many areas the migration assumptions are more critical than the fertility and mortality assumptions. Hence the migration assumptions can have a large effect on small populations in the long-term (e.g. the Shetland Islands where there is a small population) and also for some other areas with larger populations (e.g. East Dunbartonshire).
2.5 Central government population projections set local and regional population patterns into a national context. They are trend-based. However, it should be remembered that new local planning policies are often intended to modify past trends. Structure plans may be based on reasoned and agreed departures from the projections that seem better able to fit particular local circumstances.
2.6 Population projections, like some other types of projections, may indicate that existing trends and policies are likely to lead to outcomes which are judged undesirable. If new policies are then introduced, they may result in the original projections not being realised. However, this means the projections will have fulfilled one of their prime functions, to show the consequences of present demographic trends with sufficient notice for any necessary action to be taken.
2.7 It should be noted that as these population projections are trend based, they are less reliable in periods of rapid change. For example, the change in volume of migrants from the A8 accession1 countries to Scotland was not picked up by earlier projections.
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