In 2010, the IRS reports (
PDF) that itemized deductions totaled $1.2 trillion dollars—compared with total nationwide adjusted gross incomes of $8.1 trillion. The two biggest sources of deductions were taxes (mostly state, local, and real estate) totaling $445 billion and interest (nearly all on home mortgages) totaling $414 billion. Third on the list were charitable contributions, at $170 billion worth of deductions.
The Market for Charitable Giving by: John A. List