The investment seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Barclays U.S. Agency Bond Index. The fund generally seeks to track the performance of the underlying index by investing at least 90% of its assets in the securities of the underlying index and in investments that provide substantially similar exposure to securities in the underlying index. The underlying index measures the performance of the agency sector of the U.S. government bond market and is comprised of investment-grade U.S. dollar-denominated bonds or debentures issued by government and government-related agencies.