title: Willingness to pay for a hearing aid: comparing the payment scale and open-ended question.
abstract: OBJECTIVE
  Different question formats elicit different willingness-to-pay (WTP) results, but there is no consensus on which method elicits the most valid WTP. In spite of the methodological controversies, WTP is a potentially valuable tool in health economics to value health services. Our general objective was to provide additional evidence on the validity of two WTP elicitation formats: the open-ended question and the payment scale.
  
  
  METHODS
  We elicited WTP for a hearing aid among hearing aid users (n = 108), using both a payment scale and an open-ended question. We compared the results from both formats. We tested criterion validity by comparing both formats with the actual out-of-pocket payment. Construct validity was tested by examining whether WTP was consistent with positive income elasticity.
  
  
  RESULTS
  The WTP results elicited with the payment scale and open-ended question were not statistically significantly different. Both formats showed good criterion validity, although the open-ended question showed a stronger association with the actual out-of-pocket payment. The open-ended format showed better construct validity, as it was influenced by family income.
  
  
  CONCLUSIONS
  The results of the present study showed that the open-ended question was more valid than the payment scale question. We, therefore, recommend that in future WTP studies on hearing aids the open-ended question is used to directly elicit WTP values. The same recommendation may apply to other studies where respondents are familiar with costs or payments for the intervention under evaluation.
authors.affiliation: Department of Clinical Epidemiology and Medical Technology Assessment, University Hospital Maastricht, Maastricht, The Netherlands. janneke.grutters@maastro.nl
authors.forename: Janneke P C
authors.initials: JP
authors.lastname: Grutters
authors.forename: Lucien J C
authors.initials: LJ
authors.lastname: Anteunis
authors.forename: Michelene N
authors.initials: MN
authors.lastname: Chenault
authors.forename: Manuela A
authors.initials: MA
authors.lastname: Joore
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005382:Financing, Personal; D006310:Hearing Aids / Q000191:economics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D011795:Surveys and Questionnaires