Estimating willingness to pay with the stochastic payment card design: further evidence from rural Cameroon

This study reports new empirical findings of the field test of the stochastic payment card (SPC) design recently proposed by Wang (Contingent valuation of environmental resources: A stochastic perspective, 1997a; Journal of Environmental Economics & Management 32:219–232, 1997b). The purpose is to see how well this new contingent valuation method (CVM) elicitation format works in different cultural contexts, and what lessons can be drawn in general regarding its usefulness in environmental valuation. The survey is designed to estimate willingness to pay (WTP) values for an intended community-based environmental project in rural Cameroon (i.e., the control of malaria using larvivorous eating fish species). In order to estimate the bid function, Heckman’s 2-step method is used to detect, and if possible, correct for sample selection bias, an issue overlooked by the 2-step modeling approach proposed by Wang (1997a). The results suggest generally that in the presence of sample selection bias, Heckman’s 2-step estimates are more efficient and reliable for the public project in question than Wang’s proposed 2-stage modeling approach.