@inbook{NBERc4547,
 Crossref = "NBERbrow08-1",
 title = "Changing Progressivity as a Means of Risk Protection in Investment-Based Social Security",
 author = "Andrew A. Samwick",
 BookTitle = "Social Security Policy in a Changing Environment",
 Publisher = "University of Chicago Press",
 pages = "299-327",
 year = "2009",
 month = "June",
 URL = "http://www.nber.org/chapters/c4547",
}
@book{NBERbrow08-1,
 title = "Social Security Policy in a Changing Environment",
 author = "Jeffrey R. Brown and Jeffrey B. Liebman and David A. Wise",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "University of Chicago Press",
 year = "2009",
 URL = "http://www.nber.org/books/brow08-1",
}