Improving meta-analyses on hypothetical bias by using separate models for private and public goods

Previous meta-analyses examined hypothetical bias studies with the aim of identifying characteristics of stated preference (SP) design that potentially reduce hypothetical bias. However, previous meta-analyses combined observations for both public and private goods in their models. In this paper, we argue that eliciting values for public and private goods should be considered in separate models. Individuals’ behaviours, the choice of mechanism and the efficiency of mitigation techniques are specific to each type of good. Separating the models should allow more precise model specification and better identification of design effects. With two meta-regressions hierarchical mixed-effect models we provide the first meta-analysis for public and private goods separately. This approach provides specific information regarding SP design and better insight into the efficiency of mitigation techniques to reduce hypothetical bias.