That is because interest on municipal bonds is generally tax-exempt.Investors accept a lower yield on a muni-bond than on a comparable Treasury bond on which they pay tax.

• 那是因为市政债券的利息一般是免税地，所以相较于收税的国债，投资者愿意接受收益率更低的市政债券(原译：投资者承认相较于收税的国债，市政债券的投资收益更低)。