The Congressional Research Service (CRS) works exclusively for the United States Congress, providing policy and legal analysis to committees and Members of both the House and Senate, regardless of party affiliation. As a legislative branch agency within the Library of Congress, CRS has been a valued and respected resource on Capitol Hill for more than a century. The following link is a report they just did about Central States.
http://benefitslink.com/articles/CRS_R44355_01282016.pdf
http://benefitslink.com/articles/CRS_R44355_01282016.pdf