Economics Letters 123 (2014) 252–255 Contents lists available at ScienceDirect Economics Letters journal homepage: www.elsevier.com/locate/ecolet The effect of the solemn oath script in hypothetical choice experiment survey: A pilot study Tiziana de-Magistris a,* , Stefano Pascucci b a Unidad de Economía Agroalimentaria y de los Recursos Naturales. Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA), Gobierno de Aragón. Zaragoza, Spain b Management Studies Group, Wageningen University, The Netherlands highlights • The marginal WTP estimates are statistically lower with the HO script than without the oath script. • The WTP values in the CT treatment are lower in only one out of these three attributes. • CT approach was not able to reduce the WTP values in hypothetical CEs. article info Article history: Received 19 August 2013 Received in revised form 12 February 2014 Accepted 13 February 2014 Available online 26 February 2014 JEL classification: C23 D12 Q18 Keywords: Oath script Cheap talk script Willingness-to-pay Choice experiment abstract We test the effect of the solemn oath (HO) in Hypothetical CE Survey (CE). We conducted CE surveys with three treatments: (1) CE without a cognitive task, (2) CE with a CT script, and (3) CE with a HO. Results generally suggest lower WTPs values with the HO, than without the HO script. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The Hypothetical Choice Experiment (CE) method is currently most commonly used for determining state preferences in valu- ing consumer demand for nonmarket products. However, one of the main critiques on the use of this method is the existence of hypothetical bias. We refer to hypothetical bias when individuals overstate their willingness-to-pay (WTP) in hypothetical settings, and then behave inconsistently when they do not have to back up * Correspondence to: Unidad de Economía Agroalimentaria y de los Recursos Naturales. Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA), Gobierno de Aragón CITA. Avda Montañana 930, 50009 Zaragoza, Spain. Tel.: +34 976 716305; fax: +34 976 716335. E-mail addresses: tmagistris@gmail.com, tmagistris@aragon.es (T. de-Magistris). their choice through the formation of real commitments (List and Gallet, 2001; Murphy et al., 2005). Hence, many studies have fo- cused on the development of different ex-ante correction methods for reducing the difference in WTP values between real and hypo- thetical situations. To illustrate, the cheap talk (CT) script proposed in a seminal paper by Cummings and Taylor (1999), represents one of the most successful techniques to reduce hypothetical bias by explaining to participants, prior to administration of the valua- tion questions, what possible problems overstating their WTP may lead to. On the other hand, since individuals could be tempted to answer insincerely in order to project a better self-image, or to protest against the survey (Carlsson et al., 2013), a more recent approach developed to address hypothetical bias works through usage of some ex-ante correction method, based on the elicitation of honest answers. For example, the oath (HO) script approach as proposed by Jacquemet et al. (2011a, 2013) in their seminal papers, http://dx.doi.org/10.1016/j.econlet.2014.02.016 0165-1765/© 2014 Elsevier B.V. All rights reserved.