You want rules of thumb? They exist. Moses laid out the notion of a tithe — a 10th of one's income — in Deuteronomy.

Moses's kids, however, didn't want Nintendo. Few modern charitable organizations would dare to ask for so rigorous a commitment, although some churches do. The current national standard being pushed by the not-for-profit sector is the idea of becoming a "fiver," that is, someone who gives 5 percent of income and five hours a week of time.

Filer likes the fiver standard because "it's attainable; it's doable; but it represents a significant change."

How significant? The newest Gallup study reports an average rate of giving, per household, of 2 percent of income (up from 1.5 percent in 1987). The only economic group to meet the five-percent standard was the poor. People with incomes of less than $10,000 gave 5.5 percent.

People with incomes of $50,000 to $60,000 gave 1.7 percent. Those with incomes of more than $100,000 gave 2.9 percent.
—Colin McEnroe, "Americian charity; fiver becomes standard giving formula," The Record (Kitchener-Waterloo), December 1, 1990