Willingness to Pay

Willingness to pay (WTP) is the maximum monetary amount that an individual, organization, or society is willing to spend for a unit of health benefit, such as one quality adjusted life year (QALY) or one disability adjusted life year (DALY) averted. In health economics and health technology assessment, the term is also used for the cost effectiveness threshold, the decision maker's maximum acceptable cost per unit of health gained, against which the incremental cost effectiveness ratio (ICER) of a new intervention is compared. If the ICER falls below the WTP threshold, the intervention is considered cost effective because the additional health benefit it produces is worth the additional cost. WTP can also refer to the amount individuals are willing to pay for specific health services or risk reductions, as elicited through stated preference methods such as contingent valuation or discrete choice experiments.

Health care resources are finite, and societies must decide how to allocate budgets across competing interventions that each provide different health benefits at different costs. WTP thresholds provide an explicit, quantitative basis for these allocation decisions. Without a defined threshold, there is no standard against which to judge whether a new technology represents good value for money. WTP thresholds vary across countries and health systems, reflecting differences in wealth, health system financing, and societal values. NICE in England has used a range of 25,000 to 35,000 pounds per QALY since April 2026 (previously 20,000 to 30,000 pounds), while the World Health Organization has historically suggested thresholds based on multiples of per capita gross domestic product. In the United States, commonly cited thresholds range from $50,000 to $150,000 per QALY, though no single official threshold exists. Understanding WTP is essential for anyone conducting or interpreting cost effectiveness analyses.

At the health system level, the WTP threshold is typically set or applied by the decision making body (such as NICE in England, which applies a range the government set in 2026, or a national health technology assessment agency) and reflects a judgment about the opportunity cost of spending additional resources on health care. In principle, the threshold reflects the cost at which health would be displaced by diverting resources from other uses, meaning that an intervention is cost effective only if the health it produces exceeds the health that would have been generated by spending those resources elsewhere. At the individual level, WTP can be elicited through contingent valuation surveys, which ask respondents to state the maximum amount they would pay for a specified health benefit, or through discrete choice experiments, which present respondents with choices between alternatives described by different attributes (including cost) and estimate WTP from the trade offs observed. The cost effectiveness acceptability curve plots the probability that an intervention is cost effective as a function of the WTP threshold, allowing decision makers to see how the conclusion varies across a range of plausible threshold values.

Use a WTP threshold when interpreting the results of a cost effectiveness analysis, comparing the estimated ICER to the relevant threshold to determine whether the intervention represents good value for money. Use individual level WTP elicitation when estimating the monetary value of health benefits for cost benefit analysis, when pricing health services, or when assessing the demand for new health technologies. Use cost effectiveness acceptability curves to present decision uncertainty across a range of WTP thresholds, which is especially useful when the appropriate threshold is uncertain or varies across decision makers. WTP analysis is also relevant in environmental health economics, transportation safety, and any domain where mortality or morbidity risk reductions must be valued in monetary terms.

A common mistake is applying a single WTP threshold without considering its basis or appropriateness for the specific decision context. Thresholds based on per capita GDP may not reflect the actual opportunity cost of health spending in a given country. Another error is treating the WTP threshold as a sharp cutoff rather than a range, when in practice decisions near the threshold involve considerable uncertainty and may be influenced by other factors such as disease severity, equity considerations, and innovation value. In contingent valuation studies, common biases include starting point bias (the initial amount suggested influences the final response), strategic bias (respondents overstate or understate their true WTP to influence the outcome), and hypothetical bias (stated WTP exceeds what people would actually pay). Researchers sometimes confuse willingness to pay with willingness to accept compensation for a health loss, which is typically higher due to loss aversion and endowment effects.

A cost effectiveness analysis compares a new gene therapy for a rare pediatric metabolic disorder to enzyme replacement therapy. After offsetting the lifelong enzyme replacement costs it avoids, the gene therapy adds $2.1 million in discounted lifetime costs and a projected 15 additional QALYs compared to enzyme replacement, yielding an ICER of $140,000 per QALY. Evaluated against the commonly cited U.S. threshold of $150,000 per QALY, the gene therapy is cost effective. However, a cost effectiveness acceptability curve shows that the probability of cost effectiveness is only 55% at $150,000, rising to 80% at $200,000. A separate contingent valuation study surveys 400 parents of affected children and estimates a mean individual WTP of $350,000 per QALY for this condition, reflecting the high value families place on treating a severe childhood disease. The discrepancy between the societal threshold and the individual WTP highlights the tension between population level resource allocation and the value perceived by those directly affected.