The esteemed Mr Schneier points out once again how humans tend to vastly overestimate rare risks while downplaying much more common ones; this is especially true where terrorism is concerned.

You are more likely to be struck by lightning than you are to be victimized by terrorists.

From the first link:

The Underwear Bomber is precisely the sort of story we humans tend to overreact to. Our brains aren’t very good at probability and risk analysis, especially when it comes to rare events. Our brains are much better at processing the simple risks we’ve had to deal with throughout most of our species’ existence, and much poorer at evaluating the complex risks modern society forces us to face. We exaggerate spectacular rare events, and downplay familiar and common ones.

We can see the effects of this all the time. We fear being murdered, kidnapped, raped and assaulted by strangers, when it’s far more likely that the perpetrator of such offenses is a relative or a friend. We fear school shootings, even though a school is almost always the safest place a child can be. We worry about shark attacks instead of fatal dog or pig attacks — both far more common. In the U.S., over 38,000 people die each year in car crashes; that’s as many deaths as 9/11 each and every month, year after year.

Overreacting to the rare and spectacular is natural. We tend to base risk analysis on personal story rather than on data. If a friend gets mugged in a foreign country, that story is more likely to affect how safe you feel in that country than abstract crime statistics.

Later:

I tell people that if it’s in the news, don’t worry about it. The very definition of “news” is “something that hardly ever happens.” It’s when something isn’t in the news, when it’s so common that it’s no longer news — car crashes, domestic violence — that you should start worrying.

And:

And once we’re scared, we need to “do something” — even if that something doesn’t make sense and is ineffective. We need to do something directly related to the story that’s making us scared. We implement full body scanners at airports. We pass the Patriot Act. We don’t let our children go to playgrounds unsupervised. Instead of implementing effective, but more general, security measures to reduce the overall risk, we concentrate on making the fearful story go away. Yes, it’s security theater, but it makes us feel safer.