@techreport{NBERr1812,
 title = "Population Aging, Social Security Design, and Early Retirement",
 author = "Axel Borsch-Supan",
 institution = "National Bureau of Economic Research",
 type = "Working Paper",
 series = "Reprint Series",
 number = "1812",
 year = "1993",
 month = "September",
 URL = "http://www.nber.org/papers/r1812",
 abstract = {},
}