A new study by UC Santa Barbara demographer Shelly Lundberg and economist Robert Pollak of Washington University in St. Louis examines Americans’ changing sensibilities about marriage, using economics as a measuring tool. Lundberg and Pollak contend that families with high incomes and high levels of education have the greatest incentives to maintain long-term relationships. Their findings appear in the journal The Future of Children. The researchers argue that, since the mid-20th century, marriage has morphed from an institution based on gender specialization — the man earns the income and the woman stays home to take care of the children — to a means of supporting intensive investment in children.