Under normal market conditions, the Fund seeks to achieve its investment objective by investing at least 80 percent of its net assets (including investment borrowings) in municipal debt securities that pay interest that is exempt from regular federal income taxes (collectively, Municipal Securities). Municipal Securities are generally issued by or on behalf of states, territories or possessions of the U.S. and the District of Columbia and their political subdivisions, agencies, authorities and other instrumentalities. The Funds investment advisor seeks to construct a portfolio that has a weighted average duration of 1-3 years. Duration is a mathematical calculation of the average life of a debt security (or portfolio of debt securities) that serves as a measure of its price risk.