Now that negative yields have become a reality, municipal bonds may be more important for income-seeking investors, said Jeff MacDonald, director of fixed income strategies at Fiduciary Trust Company International. 'Munis not only compare favorably to the negative yields now being offered by almost a dozen developed markets, but also against most sovereign bonds in positive territory, especially when viewed on a tax-equivalent basis,' said MacDonald. MacDonald added that for investors in higher tax brackets municipal bonds should be the cornerstone of any portfolio. MacDonald is encouraged by today's historically low default rates in the muni market despite the anxiety created by Puerto Rico and other fiscally-challenged issuers. He said he sees plenty of opportunities to add high-quality sources of yield potential.