For years now, we've been hearing that single parenthood is at the root of American poverty. If unmarried mothers would just settle down, the argument went, then our national poverty rate would go down, too. But new data show how wrong that argument is. Half of poor parents raising kids under 18 are now married, according to the report just released from the Center for Economic and Policy Research. The poverty rate for married couples with children is going up, having increased 47 percent since 2000.