What is the return on giving?

Suppose I have $1 to spend and I want to use it to make the world as rich as possible.  How far can my dollar go? Can I use $1 to to make the world $2 richer? $50 richer? $1000 richer? It’s hard to know what to even expect a priori, and people seem to have widely varying estimates. Let’s call this figure the return on giving. This seems like an important number, and I’ve seen lots of implicit speculation. I think it would be great to have much more explicit discussion, though it seems worthwhile to first clarify what exactly we are talking about. Read the rest of this entry »