Analysis: Income of the Elderly Population: 2003 (PDF)
Pages 9-14 of 16 page PDF. Excerpt: "The U.S. retirement income system -- including employment-based retirement plans, Social Security, individual savings, and postretirement employment -- can be assessed in part by examining the income of the current elderly population (age 65 and older). This article reviews the latest available data on the older population's income (from the U.S. Census Bureau's March 2004 Current Population Survey) and how it has changed over time, ...." (Employee Benefit Research Institute)
http://www.ebri.org/pdfs/0105notes.pdf