The fund invests at least 80% of its assets in investment-grade municipal bonds, as determined by a nationally recognized statistical rating organization (NRSRO) (e.g., Baa or higher by Moody's Investors Service, Inc. (Moody's)) or, if unrated, determined to be of comparable quality by the advisor. It may invest up to 20% of its assets in less-than-investment-grade bonds, as determined by an NRSRO (e.g., Baa by Moody's) or by the advisor.