Developments with ONS’s Small Area Population Estimates Project Andy Bates, Office for National Statistics

Outline of Talk Purpose of the Project Geography considerations Methodology Data sources Project developments Publication Plans

Purpose of the Project “To investigate the feasibility of producing an authoritative set of small area population estimates that would be available on a nationally consistent basis” –what geography? –which method and data sources? –what age/sex breakdown? –how accurate? –constrained to ONS LA mid-year estimates

What Geography? What is meant by a ‘small area’? –Census Output Areas –Wards (CAS/statistical/electoral) –Parishes/Communities ONS development of Super Output Areas –Lower Layers (LSOAs) –Middle Layers (MSOAs) 175,434 8,800 11,265 + –Upper Layers 34,378 7,193

Mean Crude Birth Rate Birmingham Data ranges are based on quintiles of national LSOA mean crude birth rates 641 LSOAs – average population 1,500 LSOAs © Crown Copyright (ONS GD )

Methodology Early stages of project identified potential methods Shortlist of 3 methods –Apportionment –Cohort Component –Ratio Change Initially produced ward test estimates for mid-2002 –Ratio Change identified as preferred method Subsequent evaluation in 2006 using MSOA test estimates for mid-2002 to mid-2004 (3 years) –Ratio Change method remained the preferred method Further full evaluation all 3 methods intended when 2011 Census data become available

Ratio Change method data requirements Previous population base (estimate) Age & sex information –Child Benefit –Older Persons Dataset –Patient Registers Special Population –Prisoners –UK Armed Forces –Foreign Armed Forces & dependants Data needs to be consistent over time!

Ratio Change method (1) Eg to derive MSOA ratios for 0-4 year olds by sex, we create dataset specific ratios: CB 0-4 male ratio = Year 2 dataset count (117) = ratio Year 1 dataset count (108) 0-4 male ratio = Child Benefit ratio + Patient Register ratio 2

Base population Year 1 SP x age & sex ratios SP Year 2 Population 2nd period Ratio Change method (2) Constrain to LA MYEs less SP

Checking of derived change Ratios

Key Data Sources Child Benefit –provided by HM Revenue & Customs –covers children 0-16 for whom benefit is claimed –data received at LSOA level, quinary age & sex Older Persons Dataset –provided by Department for Work and Pensions (DWP) –covers persons 65+ from number of benefit databases eg State Pension, Widows Benefit & Winter Fuel Allowance –data received at LSOA level, quinary age & sex Patient Register –provided by NHS –covers all persons registered with GP –data received at postcode level, single year of age & sex

Dataset coverage 2006 (OPD 2005) Dataset less MYE % difference

2005 Child Benefit & Patient Register counts r = MSOAs 0-14 year-olds r =

2005 OPD & Patient Register counts r = MSOAs 65+ year-olds r =

2006 Patient Registers v MYEs - Males

2006 Patient Registers v MYEs – Females

Patient Registers – 2006 List Inflation PR List Inflation Males Females Persons 7.3% 3.5% 5.4%

Limitations with the Estimates (1) Change in counts from administrative data sources may not reflect actual population change Some areas have difficult to estimate populations –Students & migrants Cumulative errors over time may occur During an intercensal period difficult to assess the accuracy of the estimates –no gold standard to compare against Greater uncertainty of accuracy at finer levels –eg at LSOA level by quinary age & sex

Limitations with the Estimates (2) However –most LSOAs/MSOAs have a stable population over time –average annual LSOA population change just +7 persons –no identified shortcomings with Ratio Change method –data sources are of good quality –good feedback from users over the quality of the estimates –belief therefore that for the majority of areas at least, the estimates should be of good quality –feedback is very welcome!

Project Developments Investigating data visualisation tools –Scalable Vector Graphics (SVG)

Mapping using Scalable Vector Graphics (SVG)

Project Developments Investigating data visualisation tools –scaleable vector graphics (svg) Extend geographical coverage of population estimates –Postcode Best Fit methodology (PBF)

Postcode Best Fit Development Consultation with users indicated demand for Ward population estimates on ‘current’ boundaries Demand for estimates for other geographies which cannot always be derived from LSOA estimates –Parliamentary Constituencies –National Parks Limited geographical availability of some data sources used in Ratio Change methodology –Child Benefit & Older Persons Dataset

Lower Layer SOA Estimates Ward Estimates LSOA estimates less the special population apportioned to Patient Register postcode counts Patient Register postcode counts aggregated to Wards ‘current’ Wards overlaid onto Patient Register postcodes Add back in special population Remove special population Postcode Best Fit methodology

Postcode Best Fit – River Catchment Areas © Crown Copyright (ONS GD )

Project Developments Investigating data visualisation tools –scaleable vector graphics (svg) Extend geographical coverage of population estimates –Postcode Best Fit methodology (PBF) Small area population estimates to become a standard and established ONS output

Project Developments Investigating data visualisation tools –scaleable vector graphics (svg) Extend geographical coverage of population estimates –Postcode Best Fit methodology (PBF) Small area population estimates to become a standard and established ONS output Consideration for the Experimental Statistics to become National Statistics in 2008

Planned Publications February 2008 revisions to mid-2001 to mid-2002 CAS ward estimates mid-2003 to mid-2005 CAS ward estimates mid-2001 to mid-2005 Statistical ward estimates revisions to MSOA Population Turnover Rates 2001/02 to 2003/ /05 MSOA Population Turnover Rates mid-2001 to mid-2005 Parliamentary Constituency & National Park estimates April 2008 mid-2006 LSOA & MSOA estimates May 2008 mid-2006 CAS Ward & ‘current’ ward estimates mid-2006 Parliamentary Constituency & National Park estimates Mid-2006 ‘final’ PCO estimates 2005/06 MSOA Population Turnover Rates

Contact Information the project team at: Find estimates at: Updated information on the NS website at:

Any Questions?