life savers

Kahneman uses the phrase “availability bias” to mean a biased judgment based on a memory that happens to be quickly available ... A striking example of availability bias is the fact that sharks save the lives of swimmers. Careful analysis of deaths in the ocean near San Diego shows that on average, the death of each swimmer killed by a shark saves the lives of ten others. Every time a swimmer is killed, the number of deaths by drowning goes down for a few years and then returns to the normal level. The effect occurs because reports of death by shark attack are remembered more vividly than reports of drownings.
From Freeman Dyson's review of Thinking, Fast and Slow by Daniel Kahneman, in the NYRB 12/22/2011.

Photo of shark teeth by Quercus Design.