earn interest set by law at the weighted average yield on outstanding US Treasury securities with four or more years to maturity. Since these securities are backed by the full faith and credit of the US Government; the G Fund is the only fund with no risk of loss of principal. The G Fund was the initial fund established by the TSP when it began operations on April 1, 1987. F Fund – Fixed Income Index fund. Invested in BlackRock's U.S. Debt Index Fund. Tracks the Bloomberg Barclays US Aggregate Bond Index. The F Fund was opened to Federal employees in January 1988 but was limited to only a portion of contributions; beginning January 1991 all restrictions on F Fund contributions were lifted. C Fund – Common Stock Index fund. Invested in BlackRock's Equity Index Fund. Replicates the total return version of the S&P 500 index. The C Fund also opened to employees in January 1988 and was subject to the same restrictions as the F Fund until January 1991. S Fund – Small Capitalization Stock Index fund. Invested in BlackRock's Extended Market Index Fund, which tracks the Dow Jones U.S. Completion TSM index. The S Fund opened to employees in May 2001. I Fund – International Stock Index fund. Invested in BlackRock's EAFE Index Fund. Replicates the net version of the MSCI EAFE index. The I Fund opened to employees in May 2001. Lifecycle Funds Lifecycle Funds (commonly referred to as L Funds) are target date funds which, over an extended period of time (typically the period between an employee's entry/re-entry into Federal service and a presumed age of 63 for first withdrawal), allow for automatic reallocation of assets from more-risky stock funds (the C, I, and S Funds) into less-risky income funds (the F and G Funds) as an employee reaches retirement age, as an employee may lack the time, interest, and/or expertise to determine suitable investments at various life stages. Originally the Lifecycle Funds were offered only in 10-year increments (those with years ending in zero). However, on July 1, 2020, the TSP introduced new Lifecycle Funds in five-year increments. The current Lifecycle Funds established, along with the corresponding estimated retirement date window, are as follows: L2065 – Retirement date of 2063 and thereafter L2060 – Retirement date between 2058 and 2062 L2055 – Retirement date between 2053 and 2057 L2050 – Retirement date between 2048 and