Record matching for census purposes in the Netherlands

1. Record matching for census purposes in the Netherlands Eric Schulte Nordholt Senior researcher and project leader of the Census Statistics Netherlands Division Social and Spatial Statistics Department Support and Development Section Research and Development ESLE@CBS.NL Joint UNECE/Eurostat Meeting on Population and Housing Censuses in Astana 4-6 June 2007

2. Contents • History of the Dutch Census • Data sources • Micro linkage • Micro integration • Social Statistical Database • Estimation aspects • Statistical confidentiality • Conclusions

3. History of the Dutch Census • TRADITIONAL CENSUS • Ministry of Home Affairs: • 1829, 1839, 1849, 1859, 1869, 1879 and 1889 • Statistics Netherlands: • 1899, 1909, 1920, 1930, 1947, 1960 and 1971 • Unwillingness (nonresponse) and reduction expenses  no more Traditional Censuses • ALTERNATIVE: VIRTUAL CENSUS • 1981 and 1991: Population Register and surveys • development 90’s: more registers → • 2001: integrated set of registers and surveys, SSD

4. Data sources • Registers: • Population Register (PR), 16 million recordsdemographic variables: sex, age, household status etc. • Jobs file, employees, 6.5 million records,and self-employed persons, 790 thousand recordsdates of job, branch of economic activity • Fiscal administration (FIBASE)jobs,7.2 million records, and pensions and life insurance benefits,2.7 million records • Social Security administrations, 2 million records,auxiliary information integration process • Surveys: • Survey on Employment and Earnings (SEE), 3 million records,working hours, place of work • Labour Force Survey (LFS),2 years: 230.000 recordseducation, occupation, (economic) activity

5. Matching process • Matching of registers and datasets to a self constructed Central Matching File • Records are identified by a surrogate identifier (RIN) • One unique table RIN-Social Security Number • Minimal set of identifying variables • Every step in the process is a deterministic match

6. Statistics Netherlands’ backbone of persons

7. Matching process • Social security number matchingCheck on date of birth and genderA valid match when no more than one of the variables year, month, day of birth and gender differ • else • Matching using other variables like postal code, house number, date of birth, gender All keys must match • else • Match on social security number without any control on other variables

8. RIN employment income, jobs education social security,.. RIN RIN RIN YearMonthBirth, gender, municipality, civil status de-identification table RIN Selection from Municipal population register Micro data with Surrogate Identifier production environment SN Municipal Population Register Micro data Services Social Statistics Database Micro data Preparation and documentation Registers Surveys de-identified micro data Direct Identifier Surrogate Identifier (RIN)

9. Example

10. Micro integration (1) The aim of micro integration is: • To check the linked data and modify incorrect records, • In such a way that the results that are to be published are of higher quality than the original sources

11. Micro integration (2) To fulfil this demand an integrated process of: • data editing, • derivation of statistical variables, • and imputation is executed

12. Micro integration (3) Constraints and limitations: • Only variables that are to be published are micro integrated • Identity rules are necessary, e.g. the same variable in two sources or a relationship between two or more variables in one or more sources • No mass imputation

13. Social Statistical Database (SSD) • Social Statistical Database (SSD): Set of integrated microdata files with coherent and detailed demographic and socio-economic data on persons, households, jobs and benefits • No remaining internal conflicting information • SSD set: • Population Register (backbone) • Integrated jobs file • Integrated file of (social and other) benefits • Surveys, e.g. LFSCombining element:RIN-person

14. Core and satellites (1) satellite satellite satellite satellite SSD-core satellite satellite satellite satellite

15. Core and satellites (2) • Core: • contains only integral register information • contains the most important demographic and socio-economic information • contains only information that is used in at least two satellites

16. Core and satellites (3) • Satellites are produced in two steps: • Copying and derivation of the relevant information from the core SSD • Adding of the unique information on a specific theme from registers and surveys

17. Conclusions SSD • The SSD diminishes the administrative burden • The SSD increases • The efficiency of statistics production • The accuracy of statistical outputs • The relevance of social statistics • The possibilities for social policy research

18. Estimation aspects • Surveys are samples from the population • If surveys are enriched with register information, estimations of the register part of the enriched survey will lead to inconsistencies with the counts from the entire register • Statistics Netherlands developed the method of consistent and repeated weighting to solve these inconsistencies

19. Statistical confidentiality IDs Variables Characteristics Administrative sources Identifiers (PINs, sex, date of birth, address) IDsVariables Household surveys PERSONS BACKBONE full range of all persons as from 1995 IDs in sources are replaced by random Record Identification Numbers (RINs)

20. Conclusions • Matching is relatively cheap • Matching is relatively quick (short production time) • Micro integration remains important • The SSD has found its place in the organisation • Repeated weighting method guarantees consistent estimates • Statistical confidentiality aspects have become very important

21. Thank you for your attention! Time for questions and discussion