The financial advantages of giving aren’t limited to individual givers. There is also evidence that donations push up income even more at the level of an entire nation’s economy. We can demonstrate this by looking at average household charity and per capita G.D.P. as they change over time. Charity and G.D.P. levels have moved together over the years. Corrected for inflation and population changes, U.S. government data show that G.D.P. per person in America has risen over the past 50 years by about 150 percent. At the same time, donated dollars per person have risen by about 190 percent.

These trends by themselves don’t tell us which force is pushing and which is pulling, however. To figure that out, we need to determine whether past values of one affect future values of the other. By using a method called vector autoregression, economists can see how changes in this year’s G.D.P. are affected by past values of both G.D.P. and charity. If an increase in last year’s charity levels correlates with a jump in this year’s G.D.P., it is logical to conclude that donating is stimulating the economy.

As in the case of individual income, the evidence is that increases in G.D.P. and giving mutually reinforce each other: Economic growth pushes up charitable giving, and charitable giving pushes up economic growth. Data from the Statistical Abstract of the United States and the Center on Philanthropy at Indiana University provide examples: In 2004, $100 in extra income per American drove about $1.47 in additional charitable giving per person. At the same time, $100 in giving stimulated more than $1,800 in increased G.D.P. This rate of social return shows that economic-multiplier effects are not limited to private investment. In short, giving plays a positive role in American economic growth. It is a good investment for our country. Some might even go so far as to say that donating to charity is a patriotic act.