The investment seeks a high and sustainable level of current income that is exempt from federal personal income taxes. The fund has no limitations on the maturity of individual securities but is expected to maintain a dollar-weighted average maturity of 10 to 25 years. At least 75% of the securities held by the fund are municipal bonds in the top three credit-rating categories as determined by a nationally recognized statistical rating organization (NRSRO) (e.g., Aaa, Aa, and A by Moody's Investors Service, Inc. (Moody's)) or, if unrated, determined to be of comparable quality by the advisor.