Goodstein also points to this USA Today article on co-habitation.
As a minister I often see people who come into my office wanting to get married who share the same address. This stresses me out and I mention it to them because the data I've seen before indicates higher divorce rates for co habitaters. According to the article my stress is only partly founded. It depends on what kind of co habitater you are that matters. Women who live only with their eventual husband have a better chance of not divorcing than those who have serially co habitated and those who don't co habitate at all. Those who serially co habitate don't do well so the question I should ask is, "How many times have you co habitated" not "Have you co habitated."
I will need to get the study because I've got to wonder why this is true. I'm assuming it has to do with commitment levels. Those who are engaged are just starting their marriage early by co habitating. This has some historical precedent where marriage was a two step process that involved the marital bed and some sort of public recognition. Engaged co habitaters are simply consummating their marriage privately before making the public pronouncement. Serial co habitaters on the other hand, could be "testing" each other out with the option of either leaving or staying. When it doesn't "work" the first time they leave and go on to the next "test" until someone finally passes. Then, a few years later, it isn't working and so with a clearly established pattern, they leave the relationship to find one more fulfilling elsewhere. That's my guess but I'll have to find out.