The mindset that shacks up is the same mindset that doesn't rule out leaving.
The mindset that wants to marry has a goal of staying and being committed. It's not the living together to 'see if it works' that results in longevity.....it's the determination to stick it out.
This is all plain silly. SILLY! To discuss marriage success rates and longevity, and leave out the question of the quality and length of the courtship (pre-marriage, and pre-co-habitation) is just crazy.
Let’s assume people move in together more casually (that is, earlier) in their relationship than if they were to get married. They know each other less well and, bingo, are less likely to stay together. The problem is a short courtship.
I lived in an area of the country for four years that was very religious – cohabitation was less socially acceptable, couples married earlier (at younger, more impulsive ages, with shorter courtships) and divorce rates were high.
Again, the key issue is quality of the courtship. If someone wanted to study couples who each knew each other for the same period of time before EITHER moving in together unmarried or moving in together married, THEN you’d have a decent argument about the superiority of one over the other.