Living in Sin before marriage

http://www.salon.com/life/broadsheet/feature/2010/03/02/living_together_marriage

Living together before marriage has been shown to have a negative effect, statistically, making divorce somewhat more likely. Perhaps this could be explained because people who live together before marriage are both more likely to accept divorce as an option and are more open to the idea that this partner is questionable (which may be the reason they tested the relationship in the first place).