There are 366 major metropolitan areas in the United States, and a comprehensive new study by the Chronicle of Philanthropy ranks them on the basis of generosity – the percentage of income the median household in each city gives to charity. According to the Chronicle, the most generous city in America is Provo, Utah, where residents typically give away 13.9 percent of their discretionary income. Boston, by contrast, ranks No. 358: In New England’s leading city, the median household donates just 2.9 percent of its income to charity.

Provo’s generosity is typical for its region. Of the 10 most generous cities in America, according to the Chronicle’s calculations, six are in Utah and Idaho. Boston’s tight-fistedness is typical too: Of the 10 stingy cities at the bottom of the list, eight are in New England – including Springfield (No. 363) and Worcester (No. 364).

What’s the matter with Massachusetts? How can residents of the bluest state, whose political and cultural leaders make much of their compassion and frequently remind the affluent that we’re all in this together, be so lacking in personal generosity? And why would charitable giving be so outstanding in places as conservative as Utah and Idaho?

The question is built on a fallacy.

Liberals, popular stereotypes notwithstanding, are not more generous and compassionate than conservatives. To an outsider it might seem plausible that Americans whose political rhetoric emphasizes “fairness” and “social justice” would be more charitably inclined than those who stress economic liberty and individual autonomy. But reams of evidence contradict that presumption, as Syracuse University professor Arthur Brooks demonstrated in his landmark 2006 book, Who Really Cares.

However durable the myth, wrote Brooks (who now heads the American Enterprise Institute, a Washington think tank), there is no getting around the data. For years, academic research and comprehensive national studies have confirmed that Americans who lean to the left politically tend to be much less charitable than those who tilt rightward. The Chronicle of Philanthropy’s new report is only the latest in a long series of studies corroborating that fact.

In 1996, for example, the wide-ranging General Social Survey asked a large sample of Americans whether “the government has a responsibility to reduce income inequality” – a key ideological litmus test. Thirty-three percent of respondents agreed; 43 percent disagreed. The two groups differed sharply in more than their politics. The conservatives – those who opposed government programs to reduce inequality – were significantly more likely to donate money to charity than the liberals. And among those who did donate, conservatives gave away, on average, four times as much money per year.

Though there is a strong link between religious belief and philanthropy, it wasn’t just churches the conservatives were giving to. “They gave more to every type of cause and charity: health charities, education organizations, international aid groups, and human welfare agencies,” Brooks noted. They even gave more “to traditionally liberal causes, such as the environment and the arts.”

None of this was what Brooks had anticipated when he began his research. “I expected to find that political liberals … would turn out to be the most privately charitable people,” he says. “So when my early findings led to the opposite conclusion, I assumed I had made some sort of technical error…. In the end, I had no option but to change my views.”

The Chronicle’s new study, which is based on IRS records from 2008 (the most recent available), accounts for regional differences in the cost of living. It calculates charitable giving only from discretionary income – the dollars left over after paying for taxes, housing, and food. But the economic differences are not nearly as significant as cultural differences. In parts of the country where conservative values dominate, charity tends to be high. Where liberalism holds sway, charity falls. “Red states are more generous than blue states,” the Chronicle concludes. The eight states that ranked the highest in charitable giving all voted for John McCain in 2008. The seven lowest-ranking states supported Barack Obama.

Of course this doesn’t mean that there aren’t generous philanthropists in New England. It doesn’t mean selfishness is unknown on the right. What it does mean is that where people are encouraged to think that solving society’s ills is primarily a job for government, charity tends to evaporate. The politics of “compassion” isn’t the same as compassionate behavior. America’s generosity divide separates those who understand the difference from those who don’t.

(Jeff Jacoby is a columnist for The Boston Globe. His website is www.JeffJacoby.com).