The criterion validity of willingness to pay methods: A systematic review and meta-analysis of the evidence

•The debate on the criterion validity of CV-WTP is a subject of ongoing concern.•The majority of published papers confirm the presence of hypothetical bias.•The assessment of the drivers of criterion validity is largely exploratory.•Estimates reported variedly, limiting analyses and clouds clarity of comparison.•The evidence on the criterion validity of CV-WTP is more mixed than is reported.