Eliciting Willingness to Pay Without Bias Using Follow-Up Certainty Statements: Comparisons Between Probably/Definitely and a 10-Point Certainty Scale

49 Pages Posted: 15 Jun 2007 Last revised: 10 Apr 2008

See all articles by Glenn C. Blomquist

Glenn C. Blomquist

University of Kentucky - Department of Economics

Karen Blumenschein

University of Kentucky - College of Pharmacy

Magnus Johannesson

Stockholm School of Economics - Department of Economics

Date Written: March 8, 2008

Abstract

Ex post mitigation of hypothetical bias using follow up certainty questions typically takes one of two forms: (1) two options, "definitely sure" and "probably sure", or (2) a 10-point scale with 10 very certain. While both have been successful in eliminating hypothetical bias from estimates of WTP, little is known about the relationship between the two. The purpose of this paper is to compare the two using data from three field experiments. We compare four types of yes responses where the types differ in the criterion used to determine if there is sufficient certainty for a hypothetical yes response to be considered a true yes response. We make several comparisons, but focus on determining which values on the 10-point scale give the same estimates of WTP as "definitely sure" hypothetical yeses and real yeses (actual purchases.) Values that produce equivalence are near 10 on the certainty scale.

Keywords: Willingness to pay, follow-up certainty statements, contingent valuation, field experiments

JEL Classification: C93, D61, I10

Suggested Citation

Blomquist, Glenn C. and Blumenschein, Karen and Johanneson, Magnus, Eliciting Willingness to Pay Without Bias Using Follow-Up Certainty Statements: Comparisons Between Probably/Definitely and a 10-Point Certainty Scale (March 8, 2008). iHEA 2007 6th World Congress: Explorations in Health Economics Paper, Available at SSRN: https://ssrn.com/abstract=993509 or http://dx.doi.org/10.2139/ssrn.993509

Glenn C. Blomquist (Contact Author)

University of Kentucky - Department of Economics ( email )

Department of Economics
Gatton Business & Economics Bldg 335
Lexington, KY 40506-0034
United States
859-257-3924 (Phone)
859-323-1920 (Fax)

HOME PAGE: http://gatton.uky.edu/faculty/blomquist/

Karen Blumenschein

University of Kentucky - College of Pharmacy ( email )

201B College of Pharmacy Building
Lexington, KY 40506-0082
United States

Magnus Johanneson

Stockholm School of Economics - Department of Economics ( email )

P.O. Box 6501
Sveavagen 65
S-113 83 Stockholm
Sweden
+46 8 736 9443 (Phone)

HOME PAGE: http://www.hhs.se/Faculty/showperson.htm?personid=198

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