I hope I can explain this without it getting too complicated. Here goes . . .

In a number of recent posts I have stressed the importance of household size / composition in determining how many new dwellings will be needed. So I thought I’d better check with the Office for National Statistics (ONS) for the correct definition, which is: “A household is defined as one person living alone, or a group of people (not necessarily related) living at the same address who share cooking facilities and share a living room, sitting room or dining area”. Which means that a group of students sharing a house would presumably be a household, but a retirement or nursing home for elderly people would be a “communal establishment”.

This is important because each household is a separate dwelling. It follows therefore that predicted household size coupled with projected population increase will be used to assess the number of new dwellings needed. The smaller the household size, then the greater the number of dwellings.

Returning to the ONS, that agency’s Table KS101EW, says that when the Census was taken in March 2011 the number of persons living in a household in Wales was 3,011,182. Table CH01, also ONS, tells us that at the Census Wales had 1,302,700 households. If we divide the number of persons living in households with the number of households we have a figure of 2.31 persons per household. Yet in its (2008-based) household size projections, Knowledge and Analytical Services (KAS), an arm of the Department for Communities and Local Government (DCLG) in London, but based in Wales, predicted a household size for 2011 of 2.23.

This difference of .08 may seem unimportant . . . until you remember that it equates to 46,764 dwellings and (x 2.31) a population of 108,025. To put that into perspective, at the 2011 Census there were just 31,600 households in Ceredigion. Also bear in mind that, due to the ONS ‘outsourcing’ household size projections to the DCLG, it is KAS projections that are used to determine how many new homes will be needed in Wales in future years. Clearly, anyone wishing to make Wales plan for more new homes than she really needs has only to underestimate household size.

I understand that new household size projections covering the next 25 years are due out any day. These projections from the KAS will be invalid from the outset if they do not start at 2.31 in 2011, because this figure comes from the Census, it is not guesswork. The new household size projections must also take into account other evidence that suggests a slowing in the rate of household size decline, if not a static household size.

These new projections must then be used to revise Local Development Plans and all other housing need projections in Wales.