Bureau of Labor Statistics. (2003, October). Retirement plans in 2003. Retrieved February 2, 2007 from http://www.bls.gov/opud/ted/2003/sept/wk5/art05.htm.
"These data are from the BLS National Compensation Survey program. Learn more in Employee Benefits in Private Industry, 2003 (PDF) (TXT), USDL 03-489."