Environmental and Resource Economics

, Volume 51, Issue 4, pp 473–496 | Cite as

Giving Stated Preference Respondents “Time to Think”: Results From Four Countries

  • Joseph CookEmail author
  • Marc Jeuland
  • Brian Maskery
  • Dale Whittington


Previous studies have found that contingent valuation (CV) respondents who are given overnight to reflect on a CV scenario have 30–40% lower average willingness-to-pay (WTP) than respondents who are interviewed in a single session. This “time to think” (TTT) effect could explain much of the gap between real and hypothetical WTP observed in experimental studies. Yet giving time to think is still rare in binary or multinomial discrete choice studies. We review the literature on increasing survey respondents’ opportunities to reflect on their answers and synthesize results from parallel TTT studies on private vaccine demand in four countries. Across all four countries, we find robust and consistent evidence from both raw data and multivariate models for a TTT effect: giving respondents overnight to think reduced the probability that a respondent said he or she would buy the hypothetical vaccines. Average WTP fell approximately 40%. Respondents with time to think were also more certain of their answers, and a majority said they used the opportunity to consult with their spouse or family. We conclude with a discussion of why researchers might be hesitant to adopt the TTT methodology.


Stated preference Hypothetical bias Contingent valuation Stated choice 


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Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Joseph Cook
    • 1
    Email author
  • Marc Jeuland
    • 2
  • Brian Maskery
    • 3
  • Dale Whittington
    • 4
    • 5
  1. 1.Evans School of Public AffairsUniversity of WashingtonSeattleUSA
  2. 2.Sanford School of Public Policy and Duke Global Health InstituteDurhamUSA
  3. 3.Policy and Economic Research UnitInternational Vaccine InstituteSeoulKorea
  4. 4.Department of Environmental Sciences and EngineeringUniversity of North Carolina at Chapel HillChapel HillUSA
  5. 5.Manchester Business SchoolManchesterUK

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