Are preferences over health states complete?

Most applied work in health economics accepts, if only implicitly, the axio m of completeness. Preferences over health states or health services are as sumed to be well formed. They are effectively 'data' waiting to be collecte d. An alternative perspective suggests that values are initially incomplete and are constructed rather than just revealed in the process of answering choice-related questions such as willingness to pay or standard gambles. Wh at might appear as measurement error may, therefore, be a more deliberate p rocess of reflection and deliberation. This paper reports on a study that a ssessed the completeness of health preferences. The results show a mixed pa ttern. For most of the sample, values were stable over repeat administratio n, suggesting completeness. However, one-third of participants deliberately changed their answers and suggested that the interview process had forced them to think about their values more deeply. While it is premature to draw conclusions from this small sample, the suggestion is that completeness ca nnot be taken for granted. Copyright (C) 2000 John Wiley & Sons, Ltd.