The fund invests at least 80% of its net assets (plus borrowings for investment purposes) in securities the income from which, in the opinion of counsel to the issuer of each security, is exempt from regular federal individual and, as applicable, the fund's state income tax. It invests in municipal securities issued by the governments of states, their political subdivisions and the District of Columbia, U.S. territories, commonwealths and possessions or by their agencies, instrumentalities and authorities.