Municipal Bond

The security pledge, not the issuer's name, determines the credit. A general obligation bond is a claim on the issuer's tax base. Unlimited-tax GOs carry a pledge to levy property or other taxes without a statutory ceiling; limited-tax GOs cap the millage rate, so debt service competes with other spending inside a fixed revenue envelope. Analysis therefore centres on the size, wealth and stability of the tax base, demographic trends, and the issuer's existing fixed costs, notably pension and other post-employment benefit obligations.

A revenue bond is closer to project finance. Debt service depends solely on net receipts of a defined enterprise: a toll road, water and sewer system, airport, port or public university. The indenture sets a flow of funds specifying the order in which gross revenues cover operating costs, debt service, reserve replenishment and surplus. Protective covenants typically include a rate covenant obliging the issuer to set charges producing coverage above a stated multiple, an additional bonds test restricting new parity debt, and a debt service reserve fund.

Interest on most US municipal bonds is excluded from federal income tax, and residents holding in-state paper are often exempt from state and local tax as well. Investors accordingly accept a lower stated coupon than on comparable taxable debt, and the gap widens as the marginal tax rate rises. The standard bridge is the taxable-equivalent yield: divide the exempt yield by one minus the investor's marginal tax rate. The result is the pre-tax yield a taxable bond would need to offer to leave the same after-tax income.

Several qualifications matter. The exemption applies to coupon interest, not to capital gains on a bond sold or redeemed above cost. Interest on certain private activity bonds is a preference item for the alternative minimum tax. Deeply discounted municipals can trigger ordinary income treatment on accretion under the de minimis rule, which depresses their prices. And some municipals, such as the Build America Bonds issued in 2009 and 2010, are fully taxable, with the subsidy delivered to the issuer instead.

The municipal market is characterised by an enormous number of small issuers and individual CUSIPs, much of it held directly by retail investors or through mutual funds and exchange-traded funds seeking tax-exempt income. That fragmentation makes secondary trading episodic: many bonds change hands rarely, quoted spreads are wide relative to Treasuries or benchmark corporates, and dealer inventories are modest. Issues are commonly sold as serial bonds with a schedule of maturities, and callable structures with ten-year par calls are routine, so refunding activity rises sharply when rates decline.

Credit enhancement historically played a large role. Monoline insurers wrapped a substantial share of new issues until the 2008 crisis exposed their own capital weakness and stripped most of them of top ratings, after which investors returned to analysing the underlying credit. Bank letters of credit, moral obligation pledges and state intercept programmes that divert aid payments to bondholders remain in use. Defaults are infrequent relative to corporates but concentrated in unenhanced revenue sectors such as land-secured, healthcare and standalone development projects.

At Level I, municipals sit within the classification of non-sovereign government debt, alongside agency and supranational issuance. Expect to place a described security correctly, identify whether the pledge is a tax base or a defined revenue stream, and state which analytical inputs follow from that distinction: tax base breadth, debt per capita, debt to assessed value and pension funding for a general obligation credit; demand elasticity, coverage ratios and covenant strength for a revenue credit.

The quantitative expectation is the after-tax comparison. Be able to move in either direction, converting an exempt yield to its taxable equivalent and converting a taxable yield to its after-tax equivalent, and to explain why an investor in a low tax bracket may rationally prefer taxable debt. Be prepared also to argue that yield spreads over Treasuries compensate for genuine default risk, illiquidity and call risk, not for taxation alone.