Do divergences between stated and actual willingness to pay signify the existence of bias in contingent valuation surveys?
The objective of this study was to determine the factors that cause divergences over time (differences) between stated willingness to pay (WTP) and actual WTP purchase behaviour;: and consider whether any divergence signifies the presence of bias in contingent valuation studies. Stated WTP for insecticide-treated bed-nets (ITNs) was elicited from a random sample of respondents using three question formats in Nigeria. The question formats were the bidding game (BG);: binary with follow-up (BWFU) and a novel structured haggling (SH) technique. The sales of the nets and a second survey were conducted 1 month after the first survey. In the second survey, factors that might explain the divergences were built into the questionnaire and these together with socio-economic variables were examined for causes of divergences in WTP. Data were analysed using non-parametric tests, testing of means and cross-tabulations.
Social Science and Medicine (2005) 60 (3) 525-536 [doi:10.1016/j.socscimed.2004.05.023]