Household projections for Scotland Hugh Mackenzie April 2014

Summary What are the household projections? How are they produced? –Five inputs –Seven steps Variant projections How to get Census data & analysis

What are household projections? Published every two years, 2012-based projections to be published on 30 July 2014 Cover a 25 year period Projections are produced by: –Council area (also SDP Areas and National Parks later in the year) –Age of head of household –Household type (based on the number of adults and children) The projections are designated as National Statistics by the UK Statistics Authority.

Input 1: Population Projections Published every two years by NRS, 2012-based population projections to be published on 14 May 2014 Use the 2012 mid-year population estimates as a base For following years, this population is aged and estimates are made for: –Numbers surviving to the next year, using mortality rates –The expected number and age/sex structure of migrants –Number of births during the year, using fertility rates applied to the number of women of childbearing age Variant projections are produced using different assumptions about fertility, life expectancy and migration.

Input 2: CE rates Proportion of the population that are resident in communal establishments By area, age group and gender Data on CE residents is collected from a range of sources:

Step 1: Calculate private household population Private household population = Total population x (1 - CE rate) By area, age group and gender for each year CE Rates are assumed to be constant Project headship rates to 2035 Calculate private household population to 2037 Calculate the raw household projection Constrain LA figures to Scottish totals Constrain to household estimates Minimum adult and child adjustments Sum LA figures to give final Scottish figures Final projections Inputs Population projections Communal establishment estimates Headship rates Household estimates Household type distribution

Input 3: Headship rates The proportion of the private household population that head a household Census data (1991, 2001 and 2011 censuses) Head of household = first adult recorded on the census form By area, age group and household type “Non-headship” rates also included (the proportion that do not head any type of household) Every person is either the head of a household or a non- head, so for each area/age group the 7 headship rates and the non-headship rate sum to 1.

Comparison of different estimates of the distribution of household sizes in Scotland

Step 2: Project headship rates When we only used two censuses, a modified two-point exponential model was used. To make use of three censuses, two sets of projected headship rates are produced using the modified two-point exponential model. i.Using 1991 and 2001 censuses ii.Using 2001 and 2011 censuses The two sets of projected headship rates need to be combined into a single set of headship rates.

Input 4: Household type distribution in 2012 Data to come from the Scottish Household Survey (SHS). Annual survey, 2012 sample size of just under 11,000 households. We make an adjustment to the data based on differences found between the SHS and the Census in 2001 and 2011.

Step 2: Project headship rates (continued) Apply weights to the two sets of projected headship rates to combine them into a single set of rates. Weights chosen to minimise the difference between the survey data and the household projection. Allows up-to-date household type data to be included into the projections.

Step 3: Calculate raw household projection Number of heads of household = Private household population * Headship rate By area, age group and household type for each year Number of heads of household = number of households Project headship rates to 2037 Calculate private household population to 2037 Calculate the raw household projection Constrain LA figures to Scottish totals Constrain to household estimates Minimum adult and child adjustments Sum LA figures to give final Scottish figures Final projections Inputs Population projections Communal establishment estimates Headship rates Household estimates Household type distribution

Step 4: Control to Scottish totals The sum of all LA projections are constrained to the Scotland projection for each year By age group and household type Project headship rates to 2037 Calculate private household population to 2037 Calculate the raw household projection Constrain council figures to Scottish totals Constrain to household estimates Minimum adult and child adjustments Sum LA figures to give final Scottish figures Final projections Inputs Population projections Communal establishment estimates Headship rates Household estimates Household type distribution

Input 5: Household estimates Produced by NRS annually Total number of households in each local authority Based on council tax data More up to date household information than the census data Two years of data used (2012 and 2013)

Step 5: Constrain to household estimates The sum of all projected households in each LA is constrained to the household estimate for 2012 and onwards is adjusted by the same proportions as 2013 Project headship rates to 2037 Calculate private household population to 2037 Calculate the raw household projection Constrain council figures to Scottish totals Constrain to household estimates Minimum adult and child adjustments Sum LA figures to give final Scottish figures Final projections Inputs Population projections Communal establishment estimates Headship rates Household estimates Household type distribution

Step 6: Minimum adult and child adjustments The minimum number of adults required to fill all households in a council is calculated This is compared to the number of adults in the private household population in that council. In areas where the minimum number exceeds the private household population, the excess number of adults is calculated and the household types adjusted to reduce the number of adults needed. The adjustment is distributed across all multi-adult household types. Similar checks and adjustments are made for children if necessary.

Step 7: Calculate Scottish Totals Final Scotland figures are calculated by adding together all the local authority figures, so that the minimum adult/child adjustments are taken into account. Project headship rates to 2037 Calculate private household population to 2037 Calculate the raw household projection Constrain council figures to Scottish totals Constrain to household estimates Minimum adult and child adjustments Sum council figures to give final Scottish figures Final projections Inputs Population projections Communal establishment estimates Headship rates Household estimates Household type distribution

Variant projections Two variant projections will be produced in addition to the principal projection: i.Low Migration ii.High Migration Project headship rates to 2037 Calculate private household population to 2037 Calculate the raw household projection Constrain council figures to Scottish totals Constrain to household estimates Minimum adult and child adjustments Sum council figures to give final Scottish figures Final projections Inputs Population projections Communal establishment estimates Headship rates Household estimates Household type distribution

Scotland’s Census Releases 1 and 2 completed Releases 3A, 3B and 3C now published covering the bulk of Ethnicity, Identity, Language and Religion topics Release 3D to be published 15 May; tables from Population and Households topics Further releases dates confirmed shortly Quick, easy (and FREE!) online access to all the data from All the standard output tables for all the available census geographies Data visualisations and maps online

Still to come… Remaining Release 3 tables – throughout year Origin-destination statistics Census microdata files (Samples of Anonymised Records) Alternative population statistics, eg workplace population Analytical reports Further details available in Outputs Prospectus on website Activity throughout 2014 to explore uses and benefits and what NRS can do to ensure you get the most out of the data Finally – come to our Census Conference in Edinburgh on 25 June. Details on

Any questions? For more info, contact: (0131) Census website: Follow NRS on