When determining which index to use and for what period, we selected the index we deemed to be a fair representation of the characteristics of the referenced market, given the information currently available.
For U.S. stock market returns, we use the Standard & Poor’s 90 Index from 1926 through March 3, 1957; the S&P 500 Index from March 4, 1957, through 1974; the Dow Jones U.S. Total Stock Market Index (formerly known as the Dow Jones Wilshire 5000 Index) from 1975 through April 22, 2005; the MSCI US Broad Market Index from April 23, 2005, through June 2, 2013; and the CRSP US Total Market Index thereafter.
For U.S. bond market returns, we use the S&P High Grade Corporate Index from 1926 through 1968; the Citigroup High Grade Index from 1969 through 1972; the Lehman Brothers U.S. Long Credit AA Index from 1973 through 1975; the Bloomberg Barclays U.S. Aggregate Bond Index from 1976 through 2009; and the Bloomberg Barclays U.S. Aggregate Float Adjusted Index thereafter.
For U.S. short-term reserves, we use the Ibbotson U.S. 30-Day Treasury Bill Index from 1926 through 1977 and the Citigroup 3-Month U.S. Treasury Bill Index thereafter.