NEW YORK — Even as the income gap widens, the wealthiest Americans are giving a smaller share of their income to charity, while poor and middle-income people are donating a larger share, according to an extensive analysis of IRS data conducted by the Chronicle of Philanthropy.

The Chronicle, a source of news of the nonprofit world, said that Americans who earned $200,000 or more reduced the share of their income they gave to charity by 4.6 percent from 2006 to 2012. Those earning less than $100,000 donated 4.5 percent more of their income, the report said.

The Chronicle’s analysis was based on tax returns filed by those who itemize, including their charitable gifts. Rankings were compiled for states and metropolitan areas based on the ratio of contributions to adjusted gross income.

According to the report, changes in giving were most pronounced in major cities, where the percentage of income donated dropped markedly between 2006 and 2012. In Philadelphia and Buffalo, N.Y., the share of income given to charity fell by more than 10 percent; there was a 9 percent drop in Los Angeles, Minneapolis-St. Paul and Washington, D.C.

Tami Phillips of the Midnight Mission, a Los Angeles charity serving homeless people, credited gifts from low- and moderate-income people for helping sustain its programs during the recession.

“It hits closer to home,” said Phillips. “Any day, they too could become homeless.”

The Chronicle noted that wealthy donors, overall, were more oriented toward support of the arts and higher education than lower-income donors, and less oriented toward support of social-service charities.

At the state level, residents of Utah were the nation’s most generous, donating $65.60 to charity for every $1,000 they earned. Mississippi, Alabama and Tennessee were next.

At the bottom of the list was New Hampshire, where residents gave $17.40 for every $1,000 they earned.