Household Projections for Northern Ireland 9 th September 2009 Dr David Marshall & Dr Jos IJpelaar Demography & Methodology Branch Northern Ireland Statistics & Research Agency

Introduction 2006-based Household projections Health Card Registration Data –Persons/household information –Use for household propensities –Use for household transition indicators Implementation in 2008-based projections

2006-Based Household Projections

Housing Growth Planning Household composition trend Census First published in January 2005 Updated using 2006-based population projections; in March 2008 NI Household Projections

Population Projections 1991 Census Household Projections Mid-Year Population Estimates Fertility, mortality and migration assumptions Registered Births Registered Deaths Estimated Migration 2001 Census Schematic Projection Process Household formation assumptions Other Sources

Household Membership Probabilities 18 Household categories –seven sizes ( persons) and three types (adults only, 1 adult with children, 2+ adults with children) 14 Age groups Projected probabilities for membership of each household category for each age-sex group Constant age-sex probability of being resident in communal

Methodology: 2-Point Exponential For p 2001 >= p 1991 For p 2001 < p 1991

Some special cases Constant probabilities for under 19s –Evidence that the trend of smaller families and more single parent households does not continue in the period Complete “households with children” with adults, remaining adults distributed over childless household types Complete couple households with females aged 75+ from single households

Subtract projected communal population

Children in households with children

Complete households- with-children with adults

Allocate remaining adults over childless households

Completing elderly couple households

Health Card Registration Data

NI Health Card Data 1.817M health records (2008) 1.775M population estimate (2008) Primary source for official migration estimates Date of Birth, Sex & Address

Health Card (2001) vs. Census Household population by age and sex

NI Health Card Data Using address database to allocate unique address identifier Household definition: all persons at same address Communal establishments: exclude all addresses with 15+ persons

NI Health Card Data - Issues Accuracy depends on notification Incomplete address information Persons not families Armed Forces List Inflation

PersonIDAgeSexHseholdIDYear P000124FHH12001 P000125FHH12002 P000226MHH12001 P000227MHH12002 P00030FHH12002 P000351MHH22001 P000352MHH32002 P000479FHH42001 P000480FHH42002 Health Card Registration Data - Example

2001 Census Households with children, Females

Health Card (2001) vs. Census Households with children, Females

Health Card Data, Females in 2 adult households (without children)

Household Transition Age-sex probability of persons in household type A in year t being in household type A,B,C… in year t+1 Does not take account of other persons in household Cannot be done using Census data

Household Transitions Example: Household type in 2008 for females who were aged in childless 2-adult households in 2007

Household Type adult2 adults3+ adults 1 adult & child 2+ adult & child Household Type adult60%15%5 %12 %8 % 2 adults8 %63 %10 %2 %16 % 3+ adults 5 %7 %80 %9 %7 % 1 adult & child 2 %1 %0 %79 %19 % 2+ adult & child 2 % 4 %6 %85 % Household Transitions Example (2) Females aged 25-29yrs, (excl. migration)

Household Transitions Example (3) Females 25-29yrs, projections with transition matrix

Left NI 2007 Stayed 2007 Stayed 2008 Arrived in NI adult12%11%10%14% 2 adults14%12% 17% 3+ adults39%33%29%35% 1 adult & child 9%12%13%5% 2+ adult & child 26%32%35%28% Total100% Household Type - Migration Females aged 25-29yrs, 2007 and 2008

Using Health Card Registration Data in 2008-based Household Projections

Census trend vs. Health Card data Males aged 4-15yrs, 1 adult & 1 child household

Census trend vs. Health Card data Males aged 4-15yrs, 1 adult & 1 child household

Census trend vs. Health Card data Males aged 4-15yrs, 1 adult & 1 child household

Further Developments 2008-based household projections will be published in Spring 2010 –Health Card data for projecting propensities Review methodology –Introduce cohort analysis with transition matrices –Constrain transitions with projected births, deaths and migration –Alternative household types? Explore use of alternative data sources –Longitudinal Study?

Household Projections for Northern Ireland 9 th September Dr David Marshall & Dr Jos IJpelaar Demography & Methodology Branch Northern Ireland Statistics & Research Agency