“They’re taking steps toward science and away from just trying to find invidious comparisons, which has plagued other studies on the geography of giving,” said Paul G. Schervish, professor emeritus at Boston College and retired director of its Center on Wealth and Philanthropy.

Professor Schervish, who was not involved in the study, reviewed the research at the request of The New York Times. “It’s the most scientific paper on it, even though I have some questions,” he said.

Top among those was where the charitable dollars were going. A Republican county like Madison County, Idaho, for example, is one of the most charitable in the nation, but the data does not show whether those dollars are going to local causes or to organizations out of the county or the state.

Here are five major points in the study, and the authors’ theories to explain them.

Republican-leaning counties are more charitable

The more Republican a county is, the more its residents report charitable contributions, the study found.

The researchers said this finding fell within the broad political tendencies of traditional Republicans who favor less government intervention and more donations from the private sector to make up for the lack of government assistance.

“Their preference is to provide for the collective good through private institutions,” said Professor Nesbit. “But we don’t know what type of institutions they’re giving to.”

Dr. Nesbit said they also did not know whether donors were being purely generous or whether they would also benefit from their donation. This relationship is called consumption philanthropy, in which people give to a religious organization or a school from which they will derive a benefit in the form of, say, a better religious education program or a new gymnasium.