Economists want to know: Do Europeans work less because they believe less in God?

A century ago, German sociologist Max Weber put forth a novel theory of economic growth. In "The Protestant Ethic and the Spirit of Capitalism," Mr. Weber argued that Calvinist ideals fostered a disciplined work-and-save attitude that accelerated the creation of wealth. The implication - that Protestant economies outperform Catholic ones - has drawn skepticism ever since.

But today, researchers are reexamining whether there might be a link between religious belief and economic performance.

In a 2003 study of nearly 60 countries, Harvard researchers Robert Barro and Rachel McCleary found that certain religious beliefs did contribute to economic growth. Notably, they concluded that a belief in hell was a slightly more potent economic spur than a belief in heaven.

Last year, Niall Ferguson, a professor of history at Harvard University, examined the connections between faith and work ethic in light of divergent trends he found in the United States and Europe.

Religious belief in North America has "been amazingly resilient" amid big economic gains, he says, disputing the notion that wealthier countries necessarily become less religious.

But abroad, Ferguson noted that a decline in European working hours coincided with a decline in faith. "Americans don't in fact do better work than Frenchmen," he wrote. "They just do more work. A lot more." Between 1979 and 1999, the average US working year lengthened by nearly 4 percent. Yet in Germany, France, and Spain, that figure dropped by at least 10 percent. "Europeans now seem to believe in holidays, not in holy days," he adds.

This divergence, Ferguson, argues, coincides with a period of European de-Christianization, and American re-Christianization. "It's extremely hard to establish a causal relationship between changes in belief and changes in economic behavior," he cautions. But, he says, "something of Weber's theory seems to work."

Material prosperity, of course, is not the point of most religious teachings. And religion is clearly not the sole determinant of economic performance. China's official atheism hasn't stopped its rapid gains. Growth has been weaker in Muslim nations, where belief in potential damnation is high. And Ferguson notes that previous generations of Americans emphasized high levels of saving. Today, he says, they "work very hard in order to consume very hard."