Original sentence: Explanations for the premium are debated between causation (based on increased productivity) and correlation (based on spousal selection).In Australia,  legally married men enjoy a premium of just over $2 an hour.In the U.Marital status and social class tend to be self-reinforcing.Married couples tend to be richer than single parents in part because of the opportunity for specialization.Specialization has a demonstrably enriching effect on families by improving efficiency, reducing training time, increasing productivity, and allowing parents to become more skillful in their divided responsibilities.Studies show support for only productivity, only selection, and both.The "marriage wage premium" is another observed economic advantage in marriage, though a direct causation between marriage and wages is not proven.This premium is the extra income that married men earn over unmarried men.Unmarried parents tend to be poorer than their married counterparts, and poor young people are more likely to become single parents.When at least one spouse is able to focus on market work or home production it will generally make sense to specialize.the premium is estimated to be an extra ten to 50 percent