Are frequent offenders more difficult to find and less willing to participate? An analysis of unit non-response in an online survey among offenders

The interpretation of research findings based on self-reported delinquency requires knowledge of how response rates depend on the attributes of potential respondents, including their prior offending. The purpose of the present study was to quantify the extent to which, in a sample of offenders, the two main determinants of non-response ? non-contact and refusal ? depend on prior offending frequency. We used binomial and multinomial regression models to assess whether frequent offenders are more difficult to contact and less willing to participate in online surveys. These hypotheses are tested on a sample of offenders who were invited by regular mail to participate in the Online Activity Space Inventory Survey (OASIS), an online survey on mobility and safety. Controlling for gender and age as potential confounders, our findings do not confirm that frequent offenders are less likely to be successfully contacted, but they do confirm that, if contacted, they are less likely to participate. Response rates in offender-based research are selective and thus potentially biased towards infrequent offenders. They generally favour conservative estimates and conclusions, implying that any associations found between crime and its predictors are likely stronger in reality.