Selectivity bias caused by protest responses in Contingent Valuation studies can be detected and corrected by means of sample selection models. This paper compares two methods: the Heckman 2-steps method and the full ML, applied to data on forest recreation - where WTP is elicited as a...

Contingent Valuation studies are often characterized by a considerable amount of protest responses, which may have an important effect on the final estimates if the protest responses are not randomly distributed across the sample. If the standard procedure of censoring protest responses is...