Americans like to think of themselves as a generous people. But the truth appears much different. Forty-five percent of Americans, including nearly four in 10 who said a generous self-identity was important to them, actually gave no money to charity in the past year, the Science of Generosity survey found. What we end up with is a nation where a relatively few people give freely and abundantly, while most of us give little or nothing, researchers report in a new book.