In this brief, SHARE grantee Mike O'Grady (NORC, University of Chicago) details the process of linking data sets, gives an overview of data linkage projects that have been undertaken to date, and considers the potential linkages that would be both relevant and useful in a post-reform environment.  Dr. O'Grady points to several key areas where linked data sets could be beneficial going forward, including the design and implementation of the ACA's health benefit exchanges, comprehension of the complex intersection of Medicare and Medicaid, and reform of the Medicare payment system.