I found the following at the National Center for Health Statistics:
Among the findings in the report: unmarried cohabitations overall are less stable than marriages. The probability of a first marriage ending in separation or divorce within 5 years is 20 percent, but the probability of a premarital cohabitation breaking up within 5 years is 49 percent. After 10 years, the probability of a first marriage ending is 33 percent, compared with 62 percent for cohabitations.
You can view a summary of the report “Cohabitation, Marriage, Divorce, and Remarriage in the United States” at: cdc.gov/nchs/pressroom/02news/div_mar_cohab.htm or view the full 103 page report at: cdc.gov/nchs/data/series/sr_23/sr23_022.pdf
I found the following statistics at: divorcereform.org/cor.html#anchor2348930
Non-US Divorce Rates:
According to the report “Profiling Canada’s Families III”, by The Vanier Institute of the Family, unmarried cohabiting couples are four times more likely to break up than married couples. “CANADIAN TREND INCLUDES FEWER LEGAL MARRIAGES” CTV.ca News Staff, NOV 29, 2004. Cited in a posting on the Smart Marriages Listserv Nov. 29, 2004.
There is a higher risk, 40 to 85%, of divorce between couples cohabiting before marriage than couples waiting until after marriage to share a home together. (Bumpass & Sweet 1995; Hall & Zhao 1995; Bracher, Stantow, Morgan & Russell 1993; DeMaris & Rao 1992 and Glen 1990) Cited in a posting on the Smart Marriages Listserv, Sep 28, 2004.
I hope this helps!!!