The investment seeks to track the investment results of the S&P Short Term National AMT-Free Municipal Bond IndexTM. The fund will invest at least 80% of its assets in the component securities of its underlying index and in investments that have economic characteristics that are substantially identical to the component securities of its underlying index and will also be permitted to invest up to 20% of its assets in certain futures, options and swap contracts, cash and cash equivalents. The index measures the performance of the short-term investment-grade, tax-exempt U.S. municipal bond market.