Hypothetical versus real preferences: results from an opportunistic field experiment.

Over recent years there has been renewed interest in cost-benefit analysis (CBA) in health care but the 'hypothetical bias' concern (i.e. the belief that WTP values overstate real preferences) is a remaining anxiety. This paper reports new empirical data comparing hypothetical and real preferences in a health care context, using the clinical setting of patient self-management (PSM) of anticoagulation (warfarin) therapy. The data offer considerable support for the use of WTP and CBAs in a self-management health care context; the hypothetical bias hypothesis is not supported by our data. The generalisability of these results to other health care settings needs to be explored.