The Fund invests at least 80% of its net assets in municipal securities whose interest is free from federal income taxes, including the federal alternative minimum tax. Although the Fund tries to invest all of its assets in tax-free securities, it is possible that up to 20% of the Funds net assets may be in securities that pay interest that may be subject to the federal alternative minimum tax and, although not anticipated, in securities that pay interest subject to other federal or state income taxes. The Fund may invest in debt and fixed income securities of any maturity. Under normal market conditions, the Fund seeks to maintain an average effective duration of two to eight years. Effective duration seeks to measure the expected sensitivity of market price to changes in interest rates, taking into account the anticipated effects of structural complexities (for example, some bonds can be prepaid by the issuer). The Fund may invest in municipal securities that are issued on a when-issued or delayed delivery basis.