A new Chronicle of Philanthropy study charting the nation’s giving pattern found that generosity varies greatly between states, regions and even metro areas.

As a state, Iowa gives a smaller percentage of its income to charity than half the country, but Des Moines residents ranked in the upper quarter of the 366 metro areas in the study.

The study, which breaks down charitable giving by zip code, found that the typical household in Utah and Mississippi gives the most, donating more than 7 percent of its income to charity. Households in Massachusetts, Maine, Vermont and New Hampshire give less than 3 percent, putting the states at the bottom of the list. Iowa fell in the lower half, with households giving about 3.9 percent of their income to charity and donating $1 billion in total.

Residents of Salt Lake City, Memphis, and Birmingham, Ala., typically give at least 7 percent of their discretionary income to charity, while those in Boston and Providence average less than 3 percent. Des Moines, which ranked 86 out of 366 metro areas, gives 3.8 percent of discretionary income to charity.

Other key findings of the study include: Middle-class Amer­i­cans gave more of their discretionary income to charities than wealthier Americans; red states give higher shares of their income than blue states, and state policies that promote giving make a difference.

The Chronicle’s study compared generosity rates after residents paid taxes, housing, food, and other necessities. The study is based on the most recent available Internal Revenue Service records of Americans who itemized their deductions and examined taxpayers who earned $50,000 or more in 2008.

To read more about the study and to view the interactive graphic about How America Gives, click here.