This report was produced by the Longitudinal Employer-Household Dynamics Program at the U.S. Census Bureau, Jeremy S. Wu, Assistant Division Chief, Data Integration Division. The report is required by the Jointly Financed Cooperative Agreement between the Census Bureau and the Social Security Administration for fiscal year 2006 (SSA agreement number BC-05-05, as amended; Census Bureau agency reference number 0084-2005-043-002-001, project account 7675084). John Abowd participated in the project in his capacity as Distinguished Senior Research Fellow at the Census Bureau (on IPA from Cornell University). Martha Stinson and Gary Benedetto are economists on the LEHD staff. In addition to the authors named above, Lisa Dragoset (Census-LEHD), Sam Hawala (Census-SRD), Karen Masken (IRS), Bryan Ricchetti (Census-LEHD), Lars Vilhuber (Census-LEHD), and Simon Woodcock (Simon Fraser University) all contributed to the research. Josep Domingo-Ferrer (University of Rovira and Virgili), Jerome Reiter (Duke University), Vicenc Torra (Artificial Intelligence Lab, University of Barcelona), and Simon Woodcock, operating with the support of the Census Bureau through a subcontract to the main Research and Development contract between the Census Bureau and Abt Associates, Inc. (Census Bureau contract number 50YABC-2-66036, task order number TO002) to Cornell University (OSP reference number 47632), provided substantial consulting on the creation of the SIPP/SSA/IRS-PUF. The National Science Foundation through Grants ITR-0427889 and SES-0339919 to Cornell University with subcontracts to the Census Bureau (Census Bureau agreement number 0063-2005-003-000-000, project account 9098000) also provided substantial support for this project.