turtlepond:

Ghost, the answer to this might be that people who co-habitate and people who do not co-habitate are different. The people who are likely to co-habitate before marriage may have a higher divorce rate regardless of whether they live together or not beforehand. Correlation is not causation.

I did not bring this up to assert causation, but to soundly refute the previous poster's claim of causation in the opposite direction, which said (and I paraphrase) that sexual inexperience before marriage leads to a higher rate of divorce. Correlation does not imply causation, but causation does imply correlation, and the correlation in this case was not in the poster's favor.