MUST uses a top-down sector approach to municipal bond investing. The fund has fixed-weight exposure to sectors that are idiosyncratically defined: core revenue (45%, consisting of power, transportation, education, and leasing revenue bonds), health care revenue bonds (20%), high quality (15%, consisting of housing and water & sewer revenue bonds), general obligation bonds (10%), and high-yield bonds (10%). Minimum credit quality varies by sector but tends to be high at AA or above in most cases, and B or above in the high-yield sector. Note that the high-quality sector has slightly lower credit requirements than all, but the high-yield sector. Maturity windows, likewise, vary by sector and skew long from 2-10 years for general obligation bonds to 10-25 years for the health care and high-yield sectors. Holdings are market value-weighted within each sector at quarterly rebalancing. In total, at least 80% of MUST is invested in revenue bonds, roughly approximating the market.