THE EFFECT OF CASH AND OTHER FINANCIAL INDUCEMENTS ON THE RESPONSE RATE OF GENERAL-PRACTITIONERS IN A NATIONAL POSTAL STUDY

Background. Low response rates are acknowledged as a potential source of bias in survey results. Response rates are a particular problem in surveys of GPs, Thus, the methods used to encourage response to mailed surveys and the influence of inducements in maximizing response rates are fundamental issues to be examined when addressing the problem of response bias. Aim. To increase the overall response rate to a nationa l study of GPs and to explore the effects of financial and non-financi al inducements on response rates. Methods. Two mailing waves of a post al questionnaire to a 20% random sample of all GPs in England and Wale s had achieved a 33% response rate. For the third mailing wave, the no n-responding GPs were then divided into a control group, a group who w ere offered a donation to charity to complete the questionnaire and a group who were offered cash. The charity and cash groups were further subdivided into pound 5 and pound 10 groups to assess the effect of th e size of the inducement offered. For the control group, a fourth wave was sent the offer of a pound 5 or pound 10 incentive. Results. Respo nse was positively affected by the offer of an inducement. Cash, howev er, had a more substantial effect than the offer of a donation to char ity. Older GPs were less likely to participate overall, whereas male G Ps were more likely to respond to a cash inducement. Doctors who had s een more patients were less likely to reply earlier and were more like ly to respond to the offer of cash. Conclusions. Primary care is going through many changes, some of which have increased the workload of th e GP. It may now be that, to achieve the response rates needed to vali date policy-related research, the offer of inducements will become a n ecessary part of the research process.