Respondent Certainty and Payment Vehicle Effect in Contingent Valuation: an Empirical Study for the Conservation of Two Endangered Species in Zakynthos Island, Greece

This paper focuses on providing evidence of what explains respondent certainty by assessing at the same time the sensitivity of the Contingent Valuation Method (CVM) to payment vehicle effect. Two different samples were collected from local residents and foreign visitors of the Zakynthos Island in Greece and a split-sample approach was employed. The elicited conservation values concerned two endangered species, the loggerhead turtle, Caretta caretta and the monk seal, Monachus monachus. In terms of policy implications, the stated Willingness-to-Pay (WTP) values confirmed that there is a potential for a range of internal funding options, which could sustain the future operation of the existing National Marine Park of Zakynthos (NMPZ). From a methodological point of view, the study explores the determinants of self-reported certainty with regard not only to different payment modes but also to attitudinal and socio-economic variables and adds evidence to the debate about the validity of CVM by testing the presence of a payment vehicle effect. The results show evidence of sensitivity of the method to the mode of payment and reveal a relationship between the chosen payment vehicle and respondents' degree of certainty.