Increased response proportions for postal questionnaires in Texas veterinarians using incentives

Incentives are used to increase response proportions to postal questionnaires. Our objective was to compare the response proportions between incentive groups receiving a $1 bill, pen, both and none with a postal questionnaire for a veterinary public health survey conducted among veterinarians in Texas. We mailed questionnaires to a random sample of veterinarians (n=683) from Texas with three types of incentives viz. $1 bill (n=118), pen (n=111), $1 bill with pen (n=114), and questionnaire only (n=340). A total of 303 (44%; 95% confidence interval, CI: 41-48) responses were received with the lowest response proportion of 37% (95% CI: 32-43) in the no incentive group and highest response proportion of 57% (95% CI: 47-66) in $1 bill incentive group. Compared to no incentive, the response proportions were significantly higher (P<0.01) in groups receiving $1 bill, $1 bill with pen, and all incentives combined ($1 bill, a pen or both). The addition of a pen only did not improve response proportion. These findings support the use of $1 bill but not a pen alone as an effective incentive to increase response proportions to a postal questionnaire.