Strategy. To pursue its goal, the fund primarily invests in investment-grade municipal securities those in the four highest credit rating categories (rated AAA to BBB- or the unrated equivalent as determined by the investment adviser) . The fund normally invests at least 80% of its net assets (including, for this purpose, any borrowings for investment purposes) in municipal securities the interest from which is exempt from federal income tax, including the federal alternative minimum tax (AMT). The fund may invest in fixed-, variable- or floating-rate securities from municipal issuers around the country and in U.S. territories and possessions. These may include general obligation issues, which typically are backed by the issuers ability to levy taxes, and revenue issues, which typically are … Show more… To pursue its goal, the fund primarily invests in investment-grade municipal securities those in the four highest credit rating categories (rated AAA to BBB- or the unrated equivalent as determined by the investment adviser) . The fund normally invests at least 80% of its net assets (including, for this purpose, any borrowings for investment purposes) in municipal securities the interest from which is exempt from federal income tax, including the federal alternative minimum tax (AMT). The fund may invest in fixed-, variable- or floating-rate securities from municipal issuers around the country and in U.S. territories and possessions. These may include general obligation issues, which typically are backed by the issuers ability to levy taxes, and revenue issues, which typically are backed by a stream of revenue from a given source, such as an electric utility or a public water system. The fund may invest more than 25% of its total assets in municipal securities financing similar projects, such as those relating to education, health care, transportation and utilities and may also invest in municipal notes. The funds securities may carry credit enhancements (such as bond insurance) or liquidity enhancements (such as a letter of credit), which are designed to provide incremental levels of creditworthiness or liquidity. In choosing securities, the funds investment adviser seeks to maximize current income within the limits of the funds credit and maturity standards. The investment advisers credit research department analyzes and monitors the securities that the fund owns or is considering buying. The fund may invest up to 15% of its assets in below investment grade bonds (sometimes called junk bonds) that are rated, at the time of investment, at least B by at least one nationally recognized statistical rating organization or are the unrated equivalent as determined by the investment adviser. If a bond is downgraded below B or the unrated equivalent, the fund may continue to hold it unless the investment adviser determines the risk of holding the bond is unacceptable when compared to the bonds total return potential. The investment adviser may adjust the funds holdings based on actual or anticipated changes in interest rates or credit quality. The fund may also invest in derivative instruments, principally futures contracts. The fund typically uses futures as a substitute for taking a position in the underlying asset or as a part of a strategy designed to reduce exposure to other risks. During unusual market conditions, the fund may invest entirely in taxable securities and municipal securities whose interest is subject to federal income tax and the AMT as a temporary defensive measure. When the fund engages in such activities, the fund would not be pursuing its investment strategy and, as a result, it may not achieve its investment objective. Show less