Valuation of health changes with the contingent valuation method: a test of scope and question order effects.

In recent years, there has been a growing interest in the contingent valuation method for measurement of monetary values of various commodities. However, the validity and reliability of the method need to be examined thoroughly. This paper reports results of a test of scope and question order effects in a contingent valuation experiment in the health care field. Using three binary valuation questions, data were collected on willingness to pay for superior treatment of reflux oesophagitis. To test for scope effects, different probabilities of successful short- and long-term treatments were evaluated using a split sample approach. The presence of question order effects was tested by assigning respondents to different question orders. The contingent valuation method proved sensitive to changes in scope in that the willingness to pay increased with the probability of being free from symptoms and with a reduced risk of having a relapse once recovered. Also, regression analysis indicate that people who suffer from severe reflux oesophagitis are more willing to pay for more effective treatment. No question order effects were detected in the data.