Comparing three versions of the time tradeoff: time for a change?

This paper reports a comparative study of three formulations of the time-tradeoff (TTO) method of health valuation. One asks people to consider giving up time each day in exchange for better health. The second asks people to consider giving up time during a 12-month interval. The third is the more conventional TTO in which people are asked to contemplate a reduction in life expectancy. Questionnaires were sent to 4,087 adults selected at random from the population of Scotland. Each respondent provided a description of his or her health, and was asked to value an improvement in that health, using all three formulations of the TTO. The daily TTO appeared to be an improvement on the conventional formulation, correlating more strongly with health, eliciting responses that appeared to be more precise and obtaining information about the value of health from a far greater number of respondents. The performance of the annual TTO appeared to be only slightly inferior to that of the daily TTO.