Methodological influences on ecosystem valuation: a systematic review of contingent valuation studies

The contingent valuation method (CVM) has long been criticised for its capability in predicting the value of public goods. Split-sample studies are conducted to assess the effects of research methodologies on economic value estimation. However, there is a lack of literature that comprehensively reviews the previous works. This study addresses this knowledge gap by identifying the effect of questionnaire design and survey methods on CVM outcomes, focusing on ecosystem valuation. The preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework is adopted, and 74 previous studies are included, gathering 100 observations. The findings reveal that questionnaire design elements such as providing more detailed information, using hypothetical payments, incorporating additional questions, applying a more extensive scope of the conservation programme, and utilising dichotomous choice questions positively influence the mean willingness to pay (WTP). Regarding survey methods, results show that active users of the ecosystem exhibit higher WTP than non-users, and direct interaction with the respondents yields higher WTP outcomes. This study signifies how research methodology choices influence economic values derived from CVM, highlighting the importance of considering survey bias and aiding the development of a more effective survey instrument.