Hypothetical example of different individual experiences for patients who do and do not experience different events (benefit, harm, major harm, or other rare events).

In the specific example, there are no known predictors that identify the patients who will experience any of these events. The intervention of interest confers a benefit in one out of nine treated people, a minor harm in 6.8%, a major harm in 2.3%, and other events in 1%. On average, it costs $40 to gain 1.79 days. However, for the large majority of patients (80%) who will experience no events, good or bad, the cost is $10 and there is no gain (or loss) at all. For patients in the 10% who will get the benefit, without any harm, one has to pay only $8 per patient and each patient gains 30 days. Conversely, for patients in the 2% who experience the major harm and not the benefit, one has to pay $1,000 per patient and each patient loses 50 days.