American Sociological Review, 1988, Vol 53: 127-138) entitled, “Commitment and the Modern Union: Assessing the Link Between Premarital Cohabitation and Subsequent Marital Stability.
Author in this study found that the risk of divorce after living together is 80% higher than the risk of divorce after not living together.
If you google cohabitation and divorce rates you will come up with a lot of data that backs this up.
got a link please?