The use of monetary incentives in a community survey: impact on response rates, data quality, and cost

To assess the effect of incentive size on response rates, data quality, and cost in a digestive health status mail survey of a community sample of health plan enrollees.

The study population was selected from a database of enrollees in various health plans obligated to receive care at Park Nicollet Clinic-HealthSystem Minnesota, a large, multispecialty group in Minneapolis, Minnesota, and the nearby suburbs.

A total of 1,800 HealthSystem Minnesota enrollees were randomly assigned to receive a survey with an incentive of $5 or $2. The response rates for each incentive level were determined. Data quality, as indicated by item nonresponse and scale scores, was measured. Total cost and cost per completed survey were calculated.

The response rate among enrollees receiving $5 (74.3 percent) was significantly higher than among those receiving $2 (67.4 percent); differences were more pronounced in the first wave of data collection. Data quality did not differ between the two incentive groups. The total cost per completed survey was higher in the $5 condition than in the $2 condition.

A $5 incentive resulted in a higher response rate among a community patient sample with one mailing than did a $2 incentive. However, the response rates in the $2 condition approached the level of the $5 incentive, and costs were significantly lower when the full follow-up protocol was completed. Response rates were marginally increased by follow-up phone calls. The incentive level did not influence data quality. The results suggest if a survey budget is limited and a timeline is not critical, a $2 incentive provides an affordable means of increasing participation.