According to the White House, "Together, [the Bidens] reported adjusted gross income of $379,035. The Bidens paid $87,900 in total federal tax for 2011. They paid $13,843 in Delaware income tax and $3,614 in Virginia income tax. The Bidens contributed $5,540 to charity in 2011."
In other words, the Bidens donated less than 1.5 percent of their adjusted gross income to charity.
As documented by New York Times columnist and social science expert Nicholas Kristof, this apparent reluctance to donate to charity is somewhat of an epidemic among the liberal populace.