Using willingness to pay to value close substitutes: carrier screening for cystic fibrosis revisited.

Evidence suggests that previous uses of willingness to pay (WTP) to value close substitutes may have failed to discriminate between the alternatives being evaluated. This paper reports on the application of a new technique for measuring WTP in such contexts. The alternatives evaluated are two methods of screening for cystic fibrosis carrier status. The results suggest that the new method is more discriminating. Furthermore, the paper provides evidence, from reasons for respondents' WTP valuations and regression analyses, that the use of open-ended WTP questions is not valid. This is in line with the recommendations of a recent, influential, report on the use WTP techniques.