THE UNIVERSITY OF CHICAGO LEAVING LABOR: REVERSE MIGRATION, WELFARE CASH, AND THE SPECTER OF THE COMMODITY IN NORTHEASTERN BRAZIL A DISSERTATION SUBMITTED TO THE FACULTY OF THE DIVISION OF THE SOCIAL SCIENCES DEPARTMENT OF ANTHROPOLOGY AND THE FACULTY OF THE SCHOOL OF SOCIAL SERVICE ADMINISTRATION IN CANDIDACY FOR THE DEGREE OF DOCTOR OF PHILOSOPHY BY GREGORY DUFF MORTON CHICAGO, ILLINOIS DECEMBER 2015