what pulls our purse strings

Aidwatch pointed out yesterday that, while Americans had shelled out $560 million in donations to Haiti two and a half weeks after its earthquake, in the same amount of time we had only raised $5 million for Pakistanis suffering from the flood disaster.

At first glance, that's a staggering difference in charitability and one can't help conjecture - as Aidwatch does - what's at root of the donation gap: distance from home? unfamiliarity (due, among other things, to the fact that Pakistan is not a tourist destination)? distrust of Pakistani charities? a media bias? or is it just anti-Islam sentiment?

We'll probably never know, but Aidwatch mentions that at least part of what drives donations are the number of lives lost - and it just so happens that while Americans had given 100 times more to Haiti, Haiti had also suffered 100 times larger death toll.

There's also another explanation: randomness. Network theorists tell us that "trends" (that is, any behavior that catches on, including charitable giving for a disaster) act in random, unpredictable ways. In a complex system, it's often not one or two causes that can explain why you get an "information cascade" - rather it's a lot of small factors that add up. It's not a satisfying explanation, but it may be the closest to the truth.