Plausibility Ranges for Population Estimates

1. Plausibility Ranges for Population Estimates Focusing on ranges for children

2. Outline Aims Data sources Approaches Results for children Research on other age groups Summary of benefits

3. Aim Administrative sources High estimate of population Explore and Combine Low estimate of population

4. Data sources: Patient Register (0-15) Usually resident population aged 0 to 15 GP Patient Register Short term migrants Non-registration or registration lag for in-migrants List inflation or registration lag for out-migrants Erroneous list cleaning Multiple or duplicate NHS numbers School boarders Usual residents registered with a GP • Adjusted to remove short-term migrants and duplicate records

5. Data sources: Child benefit (0-15) Usually resident population aged 0 to 15 Child Benefit • Adjustments to the child benefit data to compensate for coverage differences were not possible. Short term immigrants Non-registration or registration lag Change of details lag for out-migrants Change of details lag for in-migrants Children living abroad Clerical claims School boarders Usual residents registered for Child Benefit

6. Data sources: Live births (age 0) Usually resident population aged 0 Live Births • The live births data has been adjusted for infant mortality (IMR). • To allow for internal migration between birth and mid-year, the live births minus IMR has been re-distributed to local authorities using Child Benefit data. Emigration between birth and mid-year Immigration between birth and mid-year Out-migrants between birth and mid-year Infant mortality In-migrants between birth and mid-year Usual residents born in LA j

7. Data sources: School Census (3-15) Usually resident population aged 3 to 15 School Census • Although the School Census was available at individual record level, it was not possible to make any adjustments for over coverage. Short term immigrants Attendance lag for immigrants Change of details lag for out-migrants Change of details lag for in-migrants Children at independent schools, pupil referral units or home educated Multiple pupil reference numbers Children aged 3 and 4 Usual residents at a state maintained school School boarders

8. Aggregate data: tolerance range approach Step 1 For example... Patient Register = 3000 High source (LA j) Difference = 400 Difference (LA j) Mid-Point = 2800 Mid-point (LA j) Child Benefit = 2600 Low source (LA j)

9. Aggregate data: tolerance range approach Step 2 Range size (LA j) = 2 x Difference (LA j) 3200 Upper limit (LA j) Difference (400) from Step 1 High source Mid-point (LA j) 2800 Range size (LA j = 800) Low source Lower limit (LA j) 2400

10. Aggregate data: tolerance range approach Step 3 Percentage range size (LA j) = Range size (LA j) / Mid-point(LA j) Size of range (% of mid-point) max % min % rank of LAs 10% of LAs 10% of LAs • Range size (%) restricted to prevent very narrow or wide ranges.

11. Record level data: linkage approach

12. Record-level sources (LA j) e.g. Patient Register e.g. School Census unlinked School Census unlinked Patient Register Linked dataset Lower limit Upper limit High linkage rate = Narrow range for LA j

13. Summary of approaches Age group Approach Source Under 1s Tolerance range Combines Patient Register and Live Births adjusted with Child Benefit 1 to 4 year olds Tolerance range Combines Patient Register and Child Benefit 5 to 7 year olds 8 to 11 year olds 12 to 15 year olds Lower limit – linkage approach Lower limit Linked Patient register and school Census (England) Upper limit Combines Patient register and Child Benefit Upper limit –Tolerance range

14. Results: data sources summary

15. Results: LA example - Adur (males)

16. Results: LA example - Adur (females)

17. Results: summary e.g. all LAs (males 8-11) • Relatively few areas with estimates out of range • Where areas have estimates out of range, often by small amount • Rare for areas to have estimates more than 5% above upper limit or below lower limit • Ranges quite narrow for ages 0 and 1-4, and more areas slightly out of range

18. Plausibility ranges for children • Plausibility ranges are proof of concept at this stage • Project allowed us to demonstrate techniques using aggregate and record level data • Results published 27 March 2012 (report and Excel-based tool) • Results were discussed with LAs at roadshows • Plan to further evaluate ranges in future

19. Research: 18-24 age group • Age at which people most likely to migrate • Sources: L2, HESA, Patient Register • Where Patient Register is lower than population estimates, these areas are predominantly university towns • Tested approach with HESA and PRDS linkage • Further work on matching required

20. Research: 25-59/64 age group • Investigated use of confidence intervals around estimates Local Labour Market Database (L2) • For quinary age groups sample size often small • Difficulty with excluding short-term migrants from latest tax-year data • Not yet able to apply a universal method for all LAs using the L2

21. Research: over retirement age group • Patient Register and Work and Pensions Longitudinal Study compared • Data sources were often very close to each other, potentially leading to ranges that were not diagnostically useful • Large differences between the sources for females aged 60-64 and males aged 65-69 • Surprising result that population estimate higher than PR and WPLS in 90+ age group

22. Summary of benefits • Gathered together metadata and research on administrative sources in one report • Knowledge of administrative sources fed back to teams quality assuring 2011 Census • Helped inform future population estimates methods (e.g. school boarders) • Evidence that small number of LAs may have had undercount of 0 & 1 year olds at 2001 Census • Ranges may be used in quality assuring estimates in future