Strategy. The funds investment process uses an analytical framework, which includes an assessment of securities expected income and capital appreciation, to seek securities with high expected returns. The portfolio managers categorize securities within the funds investment universe into component groups based on factors such as industry sector, credit rating, duration, country, and currency. The portfolio managers then calculate the expected return implied by the yield curve of each component group, while considering valuation metrics such as yield, duration, and option adjusted spreads. Finally, the portfolio managers adjust the portfolio to arrive at position weightings for each component group with the goal of building a portfolio with enhanced expected return. Under normal market conditions, the fund will invest at least 80% of … Show more… The funds investment process uses an analytical framework, which includes an assessment of securities expected income and capital appreciation, to seek securities with high expected returns. The portfolio managers categorize securities within the funds investment universe into component groups based on factors such as industry sector, credit rating, duration, country, and currency. The portfolio managers then calculate the expected return implied by the yield curve of each component group, while considering valuation metrics such as yield, duration, and option adjusted spreads. Finally, the portfolio managers adjust the portfolio to arrive at position weightings for each component group with the goal of building a portfolio with enhanced expected return. Under normal market conditions, the fund will invest at least 80% of its net assets, plus any borrowings for investment purposes, in municipal fixed income securities with interest payments exempt from federal income tax. A municipal fixed income security is a debt obligation issued by or on behalf of a state, its political subdivisions, agencies or instrumentalities, the District of Columbia or a U.S. territory or possession. Municipal securities include revenue bonds, general obligation bonds, municipal lease obligations, and industrial development bonds. The fund may use derivatives, such as futures contracts or swap agreements, to gain or limit exposures. The fund may purchase or sell when-issued, forward-settling, delayed delivery or forward commitment basis. The fund will invest primarily in investment grade securities as rated by an independent rating agency or determined by the advisor to be of comparable credit quality if a rating is unavailable. The fund may also engage in securities lending. Collateral received by the fund in connection with loaning its securities may consist of cash and U.S. government securities. Cash collateral may be invested in eligible securities, such as a government money market fund. The portfolio managers continually analyze market and financial data to make buy, sell, and hold decisions. When buying or selling a security, the portfolio managers may consider the trade-off between expected returns of the security and implementation or tax costs of the trade in an attempt to gain trading efficiencies, avoid unnecessary risk, and enhance fund performance. Show less