Towards a social discount rate for the economic evaluation of health technologies in Germany: an exploratory analysis.

Over the last decades, methods for the economic evaluation of health care technologies were increasingly used to inform reimbursement decisions. For a short time, the German Statutory Health Insurance makes use of these methods to support reimbursement decisions on patented drugs. In this context, the discounting procedure emerges as a critical component of these methods, as discount rates can strongly affect the resulting incremental cost-effectiveness ratios. The aim of this paper is to identify the appropriate value of a social discount rate to be used by the German Statutory Health Insurance for the economic evaluation of health technologies. On theoretical grounds, we build on the widespread view of contemporary economists that the social rate of time preference (SRTP) is the adequate social discount rate. For quantifying the SRTP, we first apply the market behaviour approach, which assumes that the SRTP is reflected in observable market interest rates. As a second approach, we derive the SRTP from optimal growth theory by using the Ramsey equation. A major part of the paper is devoted to specify the parameters of this equation. Depending on various assumptions, our empirical findings result in the range of 1.75-4.2% for the SRTP. A reasonable base case discount rate for Germany, thus, would be about 3%. Furthermore, we deal with the much debated question whether a common discount rate for costs and health benefits or a lower rate for health should be applied in health economic evaluations. In the German social health insurance system, no exogenously fixed budget constraint does exist. When evaluating a new health technology, the health care decision maker is obliged to conduct an economic evaluation in order to examine whether there is an economically appropriate relation between the value of the health gains and the additional costs which are given by the value of the consumption losses due to the additional health care expenditures. Therefore, a discount rate lower than the SRTP for consumption should be applied if an increase in the consumption value of health is expected. However, given the limited empirical evidence on the relationship between consumption and the value of health, it is hardly possible to make reliable forecasts of this value. Regarding the practice of the German evaluation authority, it is not recommended to use differential discounting in the base case. Instead, the issue of differential discounting should be addressed in sensitivity analyses. Reducing the discount rate for health compared to the rate for costs by a figure in the range between near 0% and 3% may be considered to be appropriate for Germany.