What to Do with “Prefer Not to Vote” Responses from Contingent Valuation Surveys?

Arrow et al. (1993), the “Blue Ribbon” panel that issued guidelines for contingent valuation, recommended that respondents to contingent valuation surveys be explicitly allowed to give ‘no-answer’ responses such as ‘don’t know / not sure / prefer not to vote (PNV)’ in addition to the typical ‘yes / no’ responses. However, they do not provide any further guidelines on what to do with such responses. A nationwide contingent valuation (CV) survey in 2011 for the purpose of obtaining welfare estimates of coastal wetland restoration in Louisiana was conducted, and 27 percent of total respondents chose the PNV option. This study identified demographic variables that affect respondents to choose PNV. More interestingly, we found that as the level of offered bid for the proposed environmental project increases, the proportion of ‘yes’ responses decreases, and proportions of ‘no’ and PNV equally increase. We also found that when PNV is compared to ‘yes’, respondents who believe the survey is consequential are less likely to choose PNV than respondents who believe the survey is inconsequential, and respondents who have no clear opinion about the consequentiality of the survey are more likely to choose PNV in both cases in which PNV is compared to ‘yes’ and in which PNV is compared to ‘no’.