Conservative Christians of all types, evangelical as well as Catholic, tend to link their conservative brand of their religion with proper moral behavior. By far the most popular context is marriage: they claim that a good, solid marriage is only possible when people acknowledge conservative Christianity's claims about the nature of marriage and gender roles. So why is it that Christian marriages, and especially conservative Christian marriages, end in divorce more often than atheist marriages?
The Barna Research Group, an evangelical Christian organization that does surveys and research to better understand what Christians believe and how they behave, studied divorce rates in America in 1999 and found surprising evidence that divorce is far lower among atheists than among conservative Christians — exactly the opposite of what they were probably expecting.
11% of all American adults are divorced
25% of all American adults have had at least one divorce
27% of born-again Christians have had at least one divorce
24% of all non-born-again Christians have been divorced
21% of atheists have been divorced
21% of Catholics and Lutherans have been divorced
24% of Mormons have been divorced
25% of mainstream Protestants have been divorced
29% of Baptists have been divorced
24% of nondenominational, independent Protestants have been divorced
27% of people in the South and Midwest have been divorced
26% of people in the West have been divorced
19% of people in the Northwest and Northeast have been divorced
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Credit should be given to George Barna, himself a conservative evangelical Christian, for at least trying to face up to these results and what they might mean: "We would love to be able to report that Christians are living very distinct lives and impacting the community, but...in the area of divorce rates they continue to be the same." According to Barna, his data raises "questions regarding the effectiveness of how churches minister to families" and challenge "the idea that churches provide truly practical and life-changing support for marriage."
http://atheism.about.com/od/atheistfamiliesmarriage/a/AtheistsDivorce.htm