Why 100 Once Is Worse Than 10 Times 10: Dread Risks versus "Continuous" Risks

People tend to react more strongly to a dread risk, a rare event that kills many people at once, than to a continuous risk, a relatively frequent event that kills many people over a longer period of time, even when both cause the same number of fatalities. This different reaction to the dread risk is often considered a bias, but we show that it is an ecologically rational strategy. In a series of simulations, we found evidence that dread risks affect the population more severely over time than continuous risks causing the same number of fatalities. This holds particularly true when the risks affect children and young adults who would have produced future offspring if they had survived longer.