With the abolition of regional plans local planning authorities will need to make their own assessments of local housing requirements. A key issue in doing this is the assumptions that they or the consultants they instruct should make in projecting household growth in their area. Assumptions about household formation rates and average household size could be critical: as has already been noted, in some cases a ‘flat’ average household size assumption could reduce the housing requirement by up to a third.

The examination of the available data at the local planning authority level is particularly important. It is clear that there have been significant local variations and a study that looked only at national averages would be of much less use to local practitioners. A key result from the 2011 census was that, for the first time in over a hundred years, average household size did not fall between censuses. The census found more people but fewer households than official projections had suggested, indicating that there had been changes in household formation patterns that had not been fully anticipated in the projections. This raises important issue for planning for housing at time when many local authorities are preparing or reviewing local plans in the light of the National Planning Policy Framework and the imminent abolition of regional plans. Questions raised include, “Should local authorities plan on the basis that household size will resume its fall or should they up assume that it stays flat, potentially implying that up to a third fewer homes will be needed over 20 year local plan period?”