Cost-effectiveness of follow-up contact for a postal survey: a randomised controlled trial

Objective: This study examines the effectiveness and costs of follow-up phone calls in improving response rates to a community survey. Methods: Non-responders to a postal survey were randomly allocated to receive a phone call or no phone call. The resources used for the development and implementation of the survey were documented. The response rates and cost per level of follow-up contact examined. Results: Follow-up phone calls led to a statistical significant increase in the number of responses to a community-wide survey, relative to no phone call. This relative increase in responses (n=62 for the follow-up phone call group versus n=1 for controls), did not increase the absolute survey response rate sufficiently (from 38.5% for two mailed surveys to 39.8% for two mailed surveys plus a phone call) to justify the phone call costs. Scenario analyses show increasing the initial response rate by 10% and conducting a second mailed survey achieves greater marginal cost savings than increasing the response rate to the second mailout or the follow-up phone calls. Conclusions: These results suggest a follow-up phone call was not cost effective. Survey research ought to primarily focus on obtaining optimal initial response rates by using strategies identified in a Cochrane meta-analytic review.