Distinguishing protest responses in contingent valuation: A conceptualization of motivations and attitudes behind them

The percentage of protesters in contingent valuation surveys is substantial–about 20% across many studies. This paper seeks to clarify the motivations behind protest responses. In addition, the question whether the estimation of willingness to pay (WTP) is more biased by the exclusion or inclusion of protest bids is yet undecided. Methodological improvements are difficult for three reasons: motivations behind protest responses are largely unclear, definitions of protest differ between studies and often only participants who state a zero WTP are asked for their reasons. Our survey on farm animal welfare (n = 1335) provides detailed motivations, two definitions and includes debriefing of all participants for their WTP. We find that protest bids are not a refusal to answer, they are neither irrational nor driven by lack of understanding. Quite the contrary, a large part of participants is directly motivated by moral reasons. Furthermore, protest responses are not coupled to a zero WTP. In our sample, only 8% out of 32% protesting participants had a zero WTP. Only a small fraction of zero bids (0.4%) are true WTP-statements, i.e. respondents were satisfied with the status quo. This finding has important implications for existing WTP-estimates which might be biased. Finally, we provide detailed estimates of the WTP for animal welfare issues by including and excluding different types of protesters and outliers.条件价值评估（Contingent Valuation, CV）调查中抗议者的占比颇高——多项研究显示该比例约为20%。本研究旨在阐明抗议回应背后的动机。此外，关于剔除或纳入抗议出价对支付意愿（Willingness to Pay, WTP）估计结果偏误影响更显著的问题，目前尚无定论。方法学改进面临三重困境：其一，抗议回应的动机尚不明确；其二，不同研究对“抗议”的定义存在差异；其三，过往研究往往仅询问声明零支付意愿的受访者的动机。本研究针对农场动物福利开展的调查（有效样本量n=1335）不仅提供了详尽的动机数据，同时涵盖两种抗议定义，并对所有受访者就其支付意愿情况进行了回溯性访谈。研究发现，抗议出价并非拒答行为，既不具有非理性特征，也并非源于受访者理解能力不足。恰恰相反，相当一部分受访者的抗议动机直接源于道德考量。此外，抗议回应与零支付意愿并不绑定。在本研究样本中，32%的抗议参与者中仅有8%声明了零支付意愿。仅有极小比例的零出价（0.4%）属于真实的支付意愿表述，即受访者对现状表示满意。该结论对现存可能存在偏误的支付意愿估计结果具有重要启示意义。最后，本研究通过纳入与排除不同类型的抗议参与者及异常值，针对动物福利相关议题的支付意愿提供了详尽的估计结果。