I found this information interesting:
(Source: The National Marriage Project, Rutgers. University, 2002)

Co-habitation among the youth is replacing marriage. Over 1/2 of those walking down the marriage aisle today have lived together first.
Here are the universities findings:

1. Living together before marriage increases the risk of breaking up after marriage.
-There's a 46% higher chance of divorce
-Co-habitators are not as committed as married couples in their dedication to the continual relationship and reclutance to terminate it and are more oriented towards their own personal autonomy.
-In living together before marriage there is the perception of "if this doesn't work for me, it's easy to leave you," therefore conflict-resolution skills are not developed.

2. Living together outrside of marriage increases the risk of domestic violence for women and increases the risk of physical and sexual abuse for children.
-The most unsafe of all family environments for children is that in which the mother is living with somebody other than the child's biological father.


3. Unmarried couples have lower levels of happiness and well-being than married couples.
-Married couples have more labor force productivity, better physical and mental health, and general happiness and longevity.
-Those entering a marriage have the mindset of being committed to each other long-term which therefore provides stability long-term.

Other statistics:
-Annual rates of depression among co-habitating couples are three times that what they are among married couples.
-Women in cohabiting relationships are more likely to suffer physical and sexual abuse.
-Aggression has shown to be twice as common among co-habitors than it is among married couples.
-Women are 9 times more likely to be killed by their partner in a co-habiting relationship than they are in a marriage.