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Willingness to pay (WTP) is increasingly being used as a measure of valuation in health technology assessment. A variety of formats for eliciting values are available, although the relative virtues of each remain the subject of methodological controversy. This article compares valuation results obtained using a WTP survey instrument in a closed-ended format with those obtained from instruments using open-ended and payment scale formats. Samples of subjects were drawn from a general population, and all were asked to value the same intervention--alternative methods of screening for colorectal cancer. It was discovered that, whereas the open-ended and payment scale formats produced broadly similar valuations, the closed-ended format produced significantly higher WTP valuations and different justifications for those valuations. It is hypothesized that anchoring and yea-saying effects explain these differences and that the closed-ended format triggers a different response mode in subjects.

Original publication





Med Decis Making

Publication Date





150 - 159


Attitude to Health, Colorectal Neoplasms, Educational Status, Female, Financing, Personal, Health Expenditures, Humans, Linear Models, Male, Mass Screening, Middle Aged, Models, Econometric, Occult Blood, Odds Ratio, Research Design, Sex Factors, Surveys and Questionnaires, United Kingdom