The Office for National Statistics (ONS) figures estimated that four million new households will be formed between 2014 and 2039, a drop of almost a quarter compared to figures published two years ago.
The household projection data is a key input into the new standard method of assessing housing need, and the new figures have prompted dramatic drops in many councils’ housing need figures when factored into the standard method.
Consultants have warned that confusion created by the new figures will lead to council plan-making being put on hold, and previously strong applications and appeal cases being undermined.
But it has emerged that the ONS plans to publish a different version of the 2016 figures on 3 December.
In the document used to explain the methodology used to produce the projections, the ONS says: "We are also planning to publish a set of variant 2016-based household projections in which household formation rates for younger adults (those aged 25 to 44 years) are higher. The purpose of this variant would be to illustrate the uncertainty in the projections around the future household formation patterns of this age group".
However, an ONS spokesman said that the variant projections "will not change the overall household projections".
The ONS’s willingness to publish "variant" projections reflects its acknowledgement of concerns about the new approach taken to drawing up the 2016-based figures. Unlike the 2014-based projections, which drew on data from as far back as the 1971 census, the 2016-based figures were compiled with statistics that only go back to 2001. Critics have said that the new projections thus ‘bake in’ the adverse consequences for household formation of housing under-delivery in this century.
In its methodology document, the ONS acknowledges those complaints. It says some respondents to its consultation on the new method thought that using data from only the 2001 and 2011 censuses would be "insufficient".
The document says: "There was a view that only using the 2001 and 2011 censuses would result in a downward trend in household formation for the younger age groups, which in turn would downplay the need for housing for younger people".
The government has already said that it "will consult on adjustments to the way housing need is calculated so it is consistent with delivering 300,000 new homes per year by the mid-2020s", and that it will do this "as soon as possible".
Andrew Lowe, senior planner at consultancy Turley, said the government should change the standard method so that it uses the "variant" figures, rather than those published last week.
"It’s hard to make a case for government not to use this data to base its standard formula on instead, if the purpose is supposed to be making a better housing market for younger people," he said. "But this [variant] is not going to be available until December and the government needs to do something between now and December to tackle the uncertainty".
To read more of Planning’s coverage of the implications of the new household projections, click here.
This article was updated at 15.30 on 28 September 2019 to include a statement received from the ONS after the initial story was published.