According to a recent Pew study, less-educated adults are less likely to realize the economic benefits associated with cohabitation:
The typical college-educated cohabiter is at least as well off as a comparably educated married adult and better off than an adult without an opposite-sex partner. By contrast, a cohabiter without a college degree typically is worse off than a comparably educated married adult and no better off economically than an adult without an opposite-sex partner.
Freakonomics editorializes, "So if you didn’t make it to college… better get married!"
The Dish 