We designed a survey that aims at estimating individual willingness-to-pay to reduce noise and air pollution arising from transportation activity near the Pyrenees in Navarre (Spain). Our participants cope with a series of contingent valuation questions and also with an economic experiment with real incentives about the same topic. Our goal is to identify several methodological problems in the valuation process coming from hypothetical bias, correlation effect and sequence effect when series of responses are requested. Our main results are that hypothetical bias is significant, because the willingness-to-pay is greater when the survey is hypothetical compared to when there is real monetary incentive. Likewise, the correlation effect also observes the same behavior since the willingness-to-pay for pollution mitigation is close to the one established for noise reduction. Finally, we have obtained mixed evidence for the sequence effect, being present only in the contingent valuation survey part.

我们设计了一项调查，旨在估计个人愿意为减少纳瓦拉（西班牙）比利牛斯山脉附近交通活动产生的噪音和空气污染而支付的费用。我们的参与者应对一系列或有估值问题，以及针对同一主题的具有真实激励的经济实验。我们的目标是在需要一系列响应时，确定估值过程中来自假设偏差、相关效应和序列效应的几个方法论问题。我们的主要结果是假设偏差是显着的，因为与实际货币激励相比，假设调查时的支付意愿更高。同样地，相关效应也观察到相同的行为，因为为减轻污染而支付的意愿接近于为减少噪音而建立的意愿。最后，我们获得了序列效应的混合证据，仅出现在或有估值调查部分。