Eliciting willingness to pay: comparing closed-ended with open-ended and payment scale formats.
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.
Frew
Emma J
EJ
Health Economics Facility, University of Birmingham, UK.
Whynes
David K
DK
Wolstenholme
Jane L
JL
D001294:Attitude to Health; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000191:economics; D004522:Educational Status; D005260:Female; D005382:Financing, Personal; D005102:Health Expenditures; D006801:Humans; D016014:Linear Models; D008297:Male; D008403:Mass Screening / Q000191:economics*; D008875:Middle Aged; D017059:Models, Econometric; D009780:Occult Blood; D016017:Odds Ratio; D012107:Research Design; D012737:Sex Factors; D011795:Surveys and Questionnaires / Q000592:standards*; D006113:United Kingdom