Over the last two decades there has been a steady increase in the number of couples choosing to live together before marriage, and many of them expect to make a commitment to each other. The catch is that a large number of them decide not to marry. The nagging question becomes, does marriage really make a difference in relationship quality over time? The Census Bureau reports that the percentage of cohabiting adults ages 25 to 34 increased from 12 percent a decade ago to 15 percent in 2018....