Do you treat your charitable giving more like shopping or investing?

A question that too few people ask (Freakonomics):

We also sometimes give because our neighbor, friend, or work colleague pressured us to give. And so we did, to make them happy, or to win a favor from them in the future.

Either way, this means we are giving not due to altruism, but for ourselves.

If we think of ourselves as savvy investors in humanity, looking for the highest return on our charitable “investment” — that is, the most help for the best charities — where should we put our money?