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Evaluating Population Sampling Frames for UK Postal Surveys: PAF vs. Consumer Register

This study explores the efficacy of various population sampling frames used in UK postal surveys, specifically analyzing the Postcode Address File (PAF) and the Consumer Register (CR), alongside the Electoral Register (ER). With support from the Office for National Statistics and conducted through the Omnibus Survey, the research examines issues of coverage, representativeness, and potential biases in survey results related to different demographics. It highlights the strengths and limitations of these sampling frames in accurately reflecting the adult population aged 18 and over in Great Britain.

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Evaluating Population Sampling Frames for UK Postal Surveys: PAF vs. Consumer Register

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  1. In search of a population sampling frame for UK postal surveys Gerry Nicolaas and Sarah Tipping

  2. Acknowledgements Our sponsors: The Socio-economic Inequalities Branch (SEIB), Office for National Statistics Our collaborators at the Office for National Statistics: Amanda Wilmot, Abigail Dewar, Zeeshan Rahman, Colin Hand

  3. Postcode Address File (PAF) • List of all addresses to which mail is sent • Small user file (less than 50 mail items per day) • 10% of addresses are non-residential • Almost complete coverage • Most commonly used sampling frame for major surveys • Sample of addresses, NOT individuals • No names!

  4. Electoral Register (ER) • List of eligible adults aged 18+ registered to vote • Can be used to sample individuals • Includes names as well as addresses • Coverage problems!

  5. Coverage problems of ER: • Does not include people who are not eligible to vote • Does not include people who fail to register • Does not include people who opt out of the publicly available version of the ER (the edited ER)

  6. Commercial alternatives: • CACI’s Consumer Register • Experian’s National Canvasse • Equifax’ ConnectSelect • EuroDirect’s Data Exchange • NB. These databases were not developed for probability sampling of the general population.

  7. CACI’s Consumer Register: • Edited Electoral Register • Supplemented with data from Claritas, DataWorks, Bounty’s market leading mother and baby file, large mail order databases • Updated quarterly • Includes names and addresses • Also includes information which could possibly be used for sampling, e.g. modelled age • Claims to be the most comprehensive database • Almost 40 million names and addresses of UK adults

  8. Design of the study: • Sample of 6,030 PAF addresses in GB selected for the ONS Omnibus Survey (April - June 2005) • Names from CACI’s Consumer Register matched to sampled PAF addresses • Omnibus interviewers collected household grid information for responding cases, including first name, sex and age • Manual matching of Consumer Register names with names from the household grid • Omnibus household grid treated as “correct”

  9. Individuals at responding addresses Correct name & address 2,350 4,436 Incorrect name & address - 1,050 Not on CR On CR

  10. Individuals at responding addresses Correct name & address 2,350 4,436 6,784 (35%) (65%) Incorrect name & address - 1,050 Not on CR On CR

  11. Individuals at responding addresses Correct name & address 2,350 4,436 (81%) 5,486 Incorrect name & address - 1,050 (19%) Not on CR On CR

  12. Characteristics of adults aged 18+ not included on the CR: • Sex distribution is not significantly different • More likely to be aged 18-24 • More likely to be renting their accommodation • More likely to have a degree

  13. If sampling adults aged 18+ from Consumer Register: • 35% of all adults aged 18+ in GB are not included on the CR • Under-representation of specific groups may bias survey results • 19% of adults sampled from CR will not be found at address

  14. BUT…….. • Is the Consumer Register a better sampling frame for general population surveys than the edited Electoral Register? • NB. 86% of adults listed on the Consumer Register were also listed on the edited Electoral Register

  15. Individuals at responding addresses Correct name & address 2,929 3,857 Incorrect name & address - 861 Not on edited ER On edited ER

  16. Individuals at responding addresses Correct name & address 2,929 3,857 6,786 (43%) (57%) Incorrect name & address - 861 Not on edited ER On edited ER

  17. Individuals at responding addresses Correct name & address 2,929 3,857 (82%) 4,718 Incorrect name & address - 861 (18%) Not on edited ER On edited ER

  18. Sample of individuals Consumer Register % 19 65 Edited ER % 18 57 Not found at address Coverage of adults aged 18+ in GB

  19. Sample of responding individuals Edited Electoral Register % 44 4 21 16 5 2,128 Consumer Register % 44 3 20 16 5 2,444 PAF % 45 6 27 18 7 3,709 Male Aged 18-24 Renting Degree Non-white Bases

  20. Conclusion: • CR has greater coverage of GB adults than edited ER • BUT • not much greater (57% on edited ER and 65% on CR) • no improvement in sample representativeness

  21. So the search continues……. • Other commercial databases? • Combine commercial databases? • Mixed mode? • Personalised and unpersonalised mailings? • ……….

  22. Limitation of study: • We have assumed that the matching rate at the individual level was the same for responding and non-responding households • BUT • this doesn’t have impact on comparison between PAF, edited ER and CR • estimated coverage rate is likely to be an overestimate

  23. For further information: • Gerry Nicolaas • tel. 020 7549 9567 • email G.Nicolaas@NatCen.ac.uk • Amanda Wilmot • tel. 020 7533 5321 • email Amanda.Wilmot@ons.gsi.gov.uk

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