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
The highest divorce rates are in the Bible Belt: "Tennessee, Arkansas, Alabama and Oklahoma round out the Top Five in frequency of divorce...the divorce rates in these conservative states are roughly 50 percent above the national average" of 4.2/1000 people. Nine states in the Northeast (Connecticut, Maine, New Hampshire, New York, Pennsylvania, Vermont, Rhode Island, New Jersey, and Maryland) have the lowest divorce rates, averaging just 3.5/1000 people.
Barna isn't the only group to arrive at these numbers. Other researchers have also found that conservative Protestants get divorced more often than other groups, even more often than "mainline" Protestants. The fact that atheists and agnostics divorce less often than other religious groups was, however, surprising to many. Some have simply refused to believe it.
http://atheism.about.com/od/atheistfamiliesmarriage/a/AtheistsDivorce.htm