Immigration security

Refugees as Weapons of Mass Destruction

Any immigration restriction, Kahneman and Tversky would say, implies a trade-off between two errors. A Type I error involves admitting a potential terrorist. A Type II error involves stopping innocent foreigners. To formulate an appropriate policy requires balancing these two risks, given their relative likelihoods and how much you care about the saved lives of residents and the disrupted lives of potential immigrants. How many innocent lives are you willing to disrupt or endanger to avoid a terrorist attack?

Kahneman and Tversky argued that when calculating probabilities, people make systematic mistakes. They do this by searching their memory for examples. If they are reminded of the attacks in Paris and Nice, they will overestimate the probability of terror. If they are exposed to the photograph of Aylan Kurdi, they might think otherwise.