The most overwhelming proof that tax incentives have a relatively minor effect on individual charity is the tremendous consistency over time of giving as a percentage of income. Although the tax code has changed frequently and dramatically over the past twenty-three years, giving as a share of personal income has hovered around 1.83 percent. This measure reached as high as 1.95 percent in 1989 and as low as 1.71 percent in 1985. The narrow range has persisted even though the top marginal tax rate has fluctuated in that period from between 28 and 70 percent.
