Dealing with ignored attributes in choice experiments on valuation of Sweden’s environmental quality objectives

In this paper we use follow-up questions to investigate whether attributes have been ignored in a choice experiment on environmental goods. This information is subsequently used in the estimation of the model by restricting the individual parameters for the ignored attributes to zero. We then separately estimate the marginal willingness to pay (WTP) for the whole sample and for those who took all attributes into account. We find no significant differences in mean marginal WTP between these two models. However, when taking the shares of respondents who considered both the environmental and the cost attributes (52 -69 percent of the respondents) into account, then the marginal WTPs for each attribute change if the respondents who ignored the attributes have a zero WTP. Hence, not taking into account whether respondents have considered the attribute could give biased welfare estimates and wrong policy implications. We also investigate whether any socioeconomic characteristics can explain who ignores attributes, and find that very few of the variables are significant, indicating that we can only partly explain the behavior.<p>