IMPROVEMENT IN CUMULATIVE RESPONSE RATES FOLLOWING IMPLEMENTATION OF A FINANCIAL INCENTIVE

Risk estimates arising from case-control studies can be unreliable if the level of response to mailed questionnaires is inadequate. Several studies have reported improved early response rates to mailed question naires following the implementation of financial incentives. Improveme nts in cumulative response rates at the completion of the follow-up pe riod, however, have not been as pronounced. A financial incentive of $ 5.00 was implemented among control subjects in a large population-base d case-control study of Ontario, Canada, women. Required follow-up tim e and effort were decreased for the controls who received the incentiv e compared with those who did not. More importantly, cumulative respon se rates after more than 20 weeks were 20 percent higher among control s who received the incentive.