Strategy. The fund invests mainly in bonds that pay interest that is exempt from federal income tax (but that may be subject to federal alternative minimum tax (AMT)). The fund normally maintain an average dollar-weighted maturity between three and ten years. The fund may invest broadly in municipal bonds of any duration (a measure of the sensitivity of a bonds price to interest rate changes), maturity and credit quality although the bonds in which the fund invests are mainly investment-grade in quality. The fund may also invest in investments that are below-investment-grade (sometimes referred to as junk bonds), which can be more sensitive to changes in markets, credit conditions, and interest rates, and may be considered speculative. Under normal circumstances, the … Show more… The fund invests mainly in bonds that pay interest that is exempt from federal income tax (but that may be subject to federal alternative minimum tax (AMT)). The fund normally maintain an average dollar-weighted maturity between three and ten years. The fund may invest broadly in municipal bonds of any duration (a measure of the sensitivity of a bonds price to interest rate changes), maturity and credit quality although the bonds in which the fund invests are mainly investment-grade in quality. The fund may also invest in investments that are below-investment-grade (sometimes referred to as junk bonds), which can be more sensitive to changes in markets, credit conditions, and interest rates, and may be considered speculative. Under normal circumstances, the fund invests at least 80% of the funds net assets in tax-exempt investments. Investments paying interest subject to the federal AMT for individuals are considered tax-exempt investments for purposes of this policy. This investment policy cannot be changed without the approval of the funds shareholders. The fund may invest up to 20% of its net assets in securities the income on which is subject to federal income tax and may invest without limit in investments the income on which is subject to the AMT. The Investment Manager may consider, among other factors, credit, interest rate and prepayment risks, as well as general market conditions, when deciding whether to buy or sell investments. Show less