Wealthiest Donors Gave 9 Percent of Their Income in 2007, Study Finds

* Those who provided free professional services, meanwhile, gave more to charity ($158,194) than did volunteers who performed other kinds of tasks.

* Wealthy donors frequently switch their support from one charity to another. In 2007, 38 percent of rich people stopped supporting one charity, while another 43 percent stopped giving to two or three groups to which they had previously donated.