Implications of an economic model of health states worse than dead.

We introduce a formal definition of health equivalent to dead into a standard model to develop previously unrecognized insights. We find that the health state viewed as equivalent to dead will depend on an individual's health prognosis, probability of survival, and rate of time preference. Our work on maximum endurable time shows that using QALY scores based on long-run preferences to value health states that last for shorter periods can alter cardinal and ordinal valuations. Simulations show that errors of substantial magnitude in QALY scores can consequently result. We describe situations where biases are likely and identify possible corrections.