International Questionnaire Postal Response Rate: An experiment comparing no return postage to provision of International Postage Vouchers – "Coupon-Réponse International"

Between-groups, randomized, after-onlyThere was no difference in response rates between the group that received International Postage Vouchers and the group that did not. (p = 0.23)International Postage Vouchers – "Coupon-Réponse International" have no effect on response rates for international postal surveys.Studies of interventions to increase response rates on self-administered, postal questionnaires have manipulated a variety of variables including elements of questionnaire design and presentation, sponsorship, pre-notification, postage, envelopes, incentives, rewards, and follow-up techniques. The systematic review by Edwards et al. [1] included 292 trials including 258,315 participants and 75 different strategies for increasing response to postal questionnaires. Various types of postage, on both out-going and return envelopes affected response rate. A search of the literature by Edwards et al. did not uncover any international postal questionnaire studies in which the respondents were provided with return postage in some form.We wanted to see if providing return postage to international respondents had an effect on response rate. International Postage Vouchers – "Coupon-Réponse International", which can be exchanged at the respondents' post office for stamps, was the only form of international return postage available in Norway. Although this is a cumbersome method of providing return postage, we wanted to see if eliminating postal costs that might be a barrier for some respondents would have an effect. In addition, we hypothesized that the gesture of providing the vouchers would serve as an incentive and it would be up to the individual how to use the vouchers, either for returning the questionnaire or to redeem stamps for personal use.The study population comprised journalists in the health field, broadly defined. Of the 100 journalists to whom paper questionnaires were sent, names and postal addresses of the first 62 on the convenience sample list were obta