Response aggregation to obtain truthful answers to sensitive questions: Estimating the prevalence of illegal purchases of prescription drugs

This research proposes a simple, new technique to obtain truthful answers to sensitive, categorical questions. The paired response technique (PRT) asks participants to merely report the sum of the answers to two paired questions, one baseline and one sensitive, with the answers to each question known only to the participants. The technique then statistically infers the prevalence of the sensitive characteristic and its potential drivers from the association of the baseline question with other questions in the survey. Monte Carlo simulations demonstrate the performance of the PRT under varying conditions. A representative survey (n = 4,649) in the Netherlands about legal and illegal purchases of prescription drugs to enhance sexual performance reveals that 17.4% of the target population has purchased medication to enhance sexual performance at least once. In contrast, in a control group surveyed with direct questioning, only 5.1% admit having done so. The great majority of these individuals opt to purchase illegally. Two further empirical applications, respectively, in the United States and the United Kingdom, show that the PRT reduces cognitive and affective costs of survey participation compared with a state-of-the-art randomized response technique for categorical questions.