The Fund is an exchange-traded fund (ETF) that pursues its investment objective by investing in debt securities issued by the U.S. Treasury (which we refer to as U.S. Government Bonds) as well as money market funds that invest exclusively in U.S. Government Bonds or repurchase agreements collateralized by such S-6 securities. Securities issued by the U.S. Treasury historically have not had credit-related defaults (i.e., failures to fulfill payment-related obligations such as interest or principal payments) and therefore such securities are generally considered to be credit risk-free (i.e., free of the risk of non-payment of either interest or principal). When constructing its portfolio of U.S. Government Bonds, the Fund seeks to select bonds with particular durations, maturities and other investment characteristics, and in such amounts, that enable the Fund to lock in interest rates and reliably sustain its planned distributions. The Fund primarily seeks to buy bonds with maturities not longer than 20 years. As of the date of this prospectus, the average duration (which is a measure of a bonds sensitivity to interest rates) of the Funds U.S. Government Bonds is approximately 6.6 years.