What can we learn from Giffords shooting? By itself, not much

After a tragedy like the attack on Rep. Gabrielle Giffords last week, the immediate impulse to is figure out why it happened, says Nate Silver at FiveThirtyEight.com. Was Jared Lee Loughner fired by political rhetoric? To what degree was mental illness a factor? Was he liberal or conservative? Was he influenced by the Tea Party?

In  fact, Silver says, assassinations and assassination attempts in this country are so rare and so overwhelmingly committed by lone individuals whose motivations, to the extent they can be discerned, vary widely, that it is impossible to draw broad conclusions from them.

It might be more useful, he suggests, to look at the much broader sample of credible threats against top elected officials. Do they rise and fall with extremes of political debate? Is there a pattern in which officials are targeted, or in the motives cited? That “would probably provide us with considerably more insight into the risks posed by assassination, domestic terrorism, and other severe forms of political violence, than any degree of scrutiny of Mr. Loughner’s case could on its own.”