4-3. Choice is a special case of comparati¨e ¨aluation, whereas pricing or the setting
of WTP. is normally done by considering a problem in isolation. The different contexts
of choice and pricing explain some preference re¨ersals between the two tasks. The
analysis of context effects in the preceding section helps explains preference
reversals between choice and SWTP that were reported by Kahneman and Ritov
1994.. Seven critical pairs of items were constructed, each including one ecological
issue and one public health problem. The responses of two groups of respondents
were compared. One group encountered both items in a questionnaire that elicited
statements of WTP for interventions to alleviate each of several 12]14. problems,
which the respondents were instructed to consider independently. Other respondents
were asked to make a choice between two items from the same list. They
were told that ‘‘It sometimes happens that budget constraints force a choice
between two desirable projects. One has to be given up, at least for now, so that
the other can go forward.’’ The respondents were then asked which of the two
interventions they would retain, if they had to make this choice.