I'm doing a little research today and came across this US Today article from last year:
Christians question divorce rates of faithful
"It's been proclaimed from pulpits and blogs for years — Christians divorce as much as everyone else in America. But some scholars and family activists are questioning the oft-cited statistics, saying Christians who attend church regularly are more likely to remain wed. "It's a useful myth," said Bradley Wright, a University of Connecticut sociologist who recently wrote "Christians Are Hate-Filled Hypocrites ... and Other Lies You've Been Told." "Because if a pastor wants to preach about how Christians should take their marriages more seriously, he or she can trot out this statistic to get them to listen to him or her."