The accuracy of proxy responses in a stated choice setting

Abstract

Data is typically gathered from an individual respondent who represents the group or the household. This individual is often identified as the “primary decision maker” and is often asked to provide responses as a proxy for the group as the cost of interviewing each member individually is impractical and/or expensive. The collection of joint preferences is rarely done (Arora 2006) and indeed in terms of travel behaviour research the use of proxy responses is not uncommon (Wargelin and Kostyniuk 2004, Richardson 2006). Under such a framework, there exists an assumption that the primary decision maker has perfect knowledge of other group member preferences and bargaining behaviour, and is able to synthesize this information when providing a response on their behalf. The validity of such an assumption however remains an open question, with recent research calling the reliability of proxy responses into account (Bateman and Munro 2009). In this paper, using three models estimated in willingness to pay space, we examine the accuracy of proxy responses in a stated choice experiment. We find that there is overlap between a proxy response and the own preferences of the individual providing the proxy choice, that the proxy responses fail to represent the full preference heterogeneity that exists in the actual choices made by individuals, and that when the preferences of another differ substantial from an individuals on preferences the proxy choice provided by that individual is a poor estimate. Overall we find that the ability of individuals to correctly predict the choice of other individuals in their household is poor and as a result proxy responses are unreliable estimators of preference.