Estimation of numbers of British medical graduates working in the National Health Service: comparison of capture–recapture analysis and exhaustive tracing

Objective: To compare the results of capture–recapture estimates and exhaustive follow-up in identifying the percentage of UK medical graduates who subsequently worked in the British National Health Service (NHS).Methods: Postal questionnaire survey of all UK-trained doctors who graduated in 1974, with up to three reminders sent to non-respondents. Further exhaustive tracing of non-respondents to obtain whole population estimates of numbers in the NHS. Capture–recapture estimation of numbers working in the NHS, using survey data and Department of Health employment records, for comparison with results from exhaustive tracing.Results: A total of 85.3% (1460/1712) of respondents were working in the NHS, but further exhaustive tracing of non-respondents revealed that only 75.9% (1758/2317) to 79.2% (1835/2317) of the whole cohort were in the NHS. By comparison, capture–recapture analysis estimated that 76.9% (1781/2317) of the cohort were in the NHS (95% CI: 75.9% to 78.0%).Conclusions: Survey data alone over...