Incorporating recent trends in
household formation into
household projections for
Scotland
Esther Roughsedge
Household Estimates and Projections Branch
National Records of Scotland (NRS)
November 2014
Outline
• Introduction to household projections for
Scotland.
• Long-term trends in household formation.
• Recent trends.
• Changes to the projections methodology for
the 2012-base household projections.
• Results
• Other relevant trends
What are household projections?
• Produced every two years – most recent set 2012-based.
• Projections of the number of households 25 years into the
future, by:
– Council area
– Age of head of household
– Household type
• Projections are based on past trends. They are not
forecasts – we don’t attempt to account for future
economic or social changes.
• Used for informing planning decisions
• Lots of overlaps in the trends and methods used in
different parts of the UK.
Trends in household formation
Percentage change since 1991
Household numbers rising faster than population…
18%
17%
16%
15%
14%
13%
12%
11%
10%
9%
8%
7%
6%
5%
4%
3%
2%
1%
0%
-1%
1991
By 2013 there were almost 18%
more households than in 1991
In constrast, the population
was just under 5 per cent
higher
1996
2001
Year
2006
2011
…more people living alone and in smaller
households…
Annual increase in number of households
…but annual household growth has levelled
off recently…
25,000
20,000
Economic
downturn began
Vacant and second
homes decreased in
2013, largely due to reclassification, causing
an apparent increase in
the number of
households.
15,000
10,000
5,000
0
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
Year
…and the fall in average household size has
levelled off
2.28
Average household size
falling but beginng to slow
even before the
reconomic downturn
2.26
Average household size
2.24
Rate of decline slowed
even further after the onset
of the economic downturn
2.22
2.20
2.18
2.16
2.14
Economic downturn began
2.12
2001
2002
2003
2004
2005
2006
2007
Year
2008
2009
2010
2011
2012
2013
What impact have these trends
had on the household
projections?
Households by type 1991, 2001 & 2011…
…including the 2011 Census data
• So in the 2010-based projections we:
– Over-projected the increase in smaller
household types
– Over-projected the reduction in larger
household types.
– Over-projected the total increase in household
numbers.
• The trends in household formation were
based on the 1991 and 2001 Censuses
only.
• We produced a number of variants,
including an ‘alternative headship’ variant
projection, which was more accurate.
For the 2012-based projections
data from the 2011 Census was
available.
So we reviewed our method to
decide how best to include this
data (and possibly other
sources)
How are the household
projections produced?
Household projections method
• Take NRS population projections;
• Subtract population living in communal
establishments, e.g. student halls, barracks,
care home);
• Project forward information on household type
(‘headship rates’), e.g. single adult, two adults
plus children
– Used to use two censuses (1991 and 2001). Used a
modified 2-point exponential function.
– Now we have the 2011 Census available as well.
Old method - trends based on 1991
and 2001 Censuses
Census
1991-2001
1981
1991
2001
2011
Year
2021
2031
2041
2011 Census data – change in trends
Census
1991-2001
1981
1991
2001
2011
Year
2021
2031
2041
Project forward newer trends only?
Census
1991-2001
2001-2011
1981
1991
2001
2011
Year
2021
2031
2041
Project longer term trend only?
Census
1991-2001
2001-2011
1991-2011
1981
1991
2001
2011
Year
2021
2031
2041
Incorporate both recent and longer term
trends - weighted using survey data
Census
1991-2001
2001-2011
Weighted
1991-2011
1981
1991
2001
2011
Year
2021
2031
2041
New method of projecting household type
• To make use of three censuses, two sets of projected headship
rates were produced using the modified two-point exponential
model.
i.
Using 1991 and 2001 Censuses
ii.
Using 2001 and 2011 Censuses
• They were combined into a single set of headship rates, using
survey data from the Scottish Household Survey.
• Weights chosen to minimise the difference between the survey
data and the household projection.
•
For 2012 the weights were 0.75 towards 2001-2011 and 0.25
towards 1991-2001.
• Allows up-to-date household type data to be included into the
projections.
– Increasingly important as we move further away from the last census.
Calculate the household projection
Number of heads of household =
Private household population * Headship rate
• This is done for each area, age group and household type for
each year
• Number of heads of household => number of households
• We make some adjustments to ensure consistency with
population projections and household estimates, which are
based on Council Tax data.
• Unchanged since previous projections.
Household projections results
Average household size is falling…
The population is ageing…
And older people are most likely to
live alone
How have the trends changed
since the previous projections?
The new set of projections are lower than
the previous set
• 2010-based household projections
(previous projections):
• +23% over next 25 years
• 531,000 new households (21,200/year)
• 2012-based household projections (new
projections):
• +17% over next 25 years
• 396,000 new households (15,800/year)
Comparison with 2010-based
projections
3,000,000
2,500,000
2010-based alternative headship projection
2010-based principal projection
Household estimates
Numberof households
2012-based principal projection
2,000,000
1,500,000
1,000,000
500,000
0
2002
2007
2012
2017
2022
Year
2027
2032
2037
Increase in young males living alone is smaller than
previously projected, also applies to young females
120,000
1 adult: male
110,000
2012 in 2012-based projection
100,000
2035 in 2010-based projection
2035 in 2012-based projection
Number of Households
90,000
80,000
70,000
60,000
50,000
40,000
30,000
20,000
10,000
0
16-24
25-34
35-44
45-54
55-64
Age Group
65-74
75-84
85+
Reduction in 3+ adult households headed by 45-64yr
olds is lower than projected previously.
120,000
110,000
Number of Households
100,000
90,000
80,000
3+ adults
2012 in 2012-based projection
2035 in 2010-based projection
2035 in 2012-based projection
70,000
60,000
50,000
40,000
30,000
20,000
10,000
0
16-24
25-34
35-44
45-54
55-64
Age Group
65-74
75-84
85+
Other relevant trends
Young adults
Source: Census
Young adults
More young adults
are living with
parents, and fewer
are living as a
couple
Source: Census
Tenure by age, 2001 & 2011
Source: Census
Tenure by age, 2001 & 2011
Source: Census
Tenure by age, 2001 & 2011
Source: Census
Trends in house-building
Source: Scottish Government Housing
Statistics for Scotland 2014
Summary - Method
• Over the past decade the growth in household
numbers has slowed.
• Our previous projections didn’t fully capture this
trend as they used only 1991 and 2001
Censuses.
• 2012-based projections use 1991, 2001 and
2011 Censuses and survey data for weighting –
they include recent and longer-term trends.
Summary - Results
• Household numbers are still increasing,
but by less than in previous projections.
• Biggest changes are among young adults:
– Fewer living alone or in couples.
– More living with parents.
– More renting.
Contact details
•
•
•
•
[email protected]
Tel 0131 3144251
www.nrscotland.gov.uk
Register for updates on ScotStat at
www.scotland.gov.uk/Topics/Statistics/
scotstat
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