Thinking, Fast and Slow

by Daniel Kahneman

You have been exposed to a disease which if contracted leads to a quick and painless death within a week. The probability that you have the disease is 1/1,000. There is a vaccine that is effective only before any symptoms appear. What is the maximum you would be willing to pay for the vaccine? Most people are willing to pay a significant but limited amount. Facing the possibility of death is unpleasant, but the risk is small and it seems unreasonable to ruin yourself to avoid it. Now consider a slight variation: Volunteers are needed for research on the above disease. All that is required is that you expose yourself to a 1/1,000 chance of contracting the disease. What is the minimum you would ask to be paid in order to volunteer for this program? (You would not be allowed to purchase the vaccine.) As you might expect, the fee that volunteers set is far higher than the price they were willing to pay for the vaccine. Thaler reported informally that a typical ratio is about 50:1. The extremely high selling price reflects two features of this problem. In the first place, you are not supposed to sell your health; the transaction is not considered legitimate and the reluctance to engage in it is expressed in a higher price. Perhaps most important, you will be responsible for the outcome if it is bad.