Normally investing at least 80% of assets in securities included in the Bloomberg U.S. 1-5 Year Treasury Bond Index. The Bloomberg U.S. 1-5 Year Treasury Bond Index is a market value-weighted index of investment-grade fixed-rate public obligations of the U.S. Treasury with maturities between one and five years. Derivative instruments that provide investment exposure to the investments above or exposure to one or more market risk factors associated with such investments are included in the fund's 80% policy, consistent with the fund's investment policies and limitations with respect to investments in derivatives. Normally maintaining a dollar-weighted average maturity that generally is expected to be three years or less, consistent with that of the index. Using statistical sampling techniques based on duration, maturity, interest rate sensitivity, security structure, and credit quality to attempt to replicate the returns of the Bloomberg U.S. 1-5 Year Treasury Bond Index using a smaller number of securities.