Stated preferences, real behaviour and anchoring: Some empirical evidence

We compare different contingent valuation question formats with each other and with observed behaviour for a non-monetary estimation task, the expecte d number of kilometers travelled by automobile. Open-ended questions, open- ended follow-up questions, dichotomous choice (DC) questions, and double-bo und DC questions are included. The single and double-bound DC questions res ult in an estimated mean about twice as high as the actual value and the op en-ended mean. The DC question overestimation seems to be due to an anchori ng effect leading to "yea-saying" behaviour. Our results about the differen ce between DC questions and open-ended questions is consistent with the pat tern observed in contingent valuations studies of the willingness to pay. O ur results indicates that DC questions seem to be associated with a general overestimation problem that is present even for simple non-monetary estima tion tasks.