Federal Thrift Savings Plan's I Fund was the best performing of the $324.1 billion plan's investment options in 2012, with an 18.62% return, according to spokeswoman Kim Weaver.
The I Fund invests in international equities.
The next-highest performance came from the S Fund, which invests in U.S. midcap stocks. The S Fund returned 18.57%.
The C Fund, which tracks S&P 500, returned 16.07%; and the F Fund, an aggregate bond fund, returned 4.29%
The G Fund — an internally managed government securities fund — gained 1.47%.
Washington-based TSP also has five lifecycle funds that were started in 2005. Their performances for calendar year 2012 ranged from 4.77% to 15.85%