Most of the fuss about this link is bogus. Maybe a higher divorce risk makes one more likely to cohabit. Or perhaps there's some outside factor that causes both. A 1998 Roper poll of 1,200 affluent Americans found that the rich are happier than Americans overall. Rich people are happier than other people.
Married people are more likely to be rich.
Roper Starch Worldwide , January 22, 1998. Cohabitors and unmarried people include many people who have good reason to be unhappy. The poor are much less likely to marry than middle or upper-class Americans. Many disabled people can't marry because they would lose benefits. The same is true for senior citizens who depend on pensions.