Blacknad ... You wrote:
"Finally, the single biggest predictor of whether someone will be charitable is their religious participation."

I want to take a "Jaws" sized bite out of much of what has been written about religious people and their generosity: So I will.

First lets separate the money "donated" to the church itself as that money, to a great extent, goes down a rathole to paying for buildings, utilities, clergy, employees, and other accouterments of the church. I'd like to see the value of those charitable donations that excludes money given to the church. Bet those numbers would change dramatically.

If one wishes to examine the vast majority of charitable giving in my country, the US, one quickly discovers that the primary motivator is income taxes and public adulation.

I've yet to see the news story about Bill Gates and Warren Buffet going to church.

And to quote Mr. Gates:
"Just in terms of allocation of time resources, religion is not very efficient. There's a lot more I could be doing on a Sunday morning."
~ TIME magazine Vol. 149, No. 2 (13 January 1997)

You might want to check out this website.
http://atheism.about.com/b/a/257812.htm
with respect to Mr. Buffet and others.

In summary: I've heard the claim before. I don't believe it.

DA Morgan