Municipal Bond

How munis work

A typical muni:

1. State or local government issues bonds to finance infrastructure (schools, water systems, transportation, hospitals) or operations.
2. Investors buy bonds at issuance or in secondary markets.
3. Issuer pays semi-annual interest at the stated coupon rate.
4. Bondholders receive principal at maturity (or upon early call, if applicable).

Municipal bonds typically have terms of 5-30 years; some longer.

Major muni types

Two main categories:

• General obligation (GO) bonds — backed by the issuer's full taxing power. State and local governments commit to raising taxes if necessary to pay these. Generally lower-risk.
• Revenue bonds — backed by specific revenue streams (toll roads, water utility fees, hospital revenue). Risk depends on the specific revenue source.

Within each category, further subcategorization by purpose, geography, and credit quality.

Tax advantages

The defining feature of munis:

• Federal tax exemption — interest is generally exempt from federal income tax.
• State tax exemption — interest from your home state's munis is typically also exempt from state tax.
• "Triple tax-free" — for some bonds in some states (e.g., NYC munis for NYC residents).

A 4% muni yields roughly equivalent to a 6% taxable bond for someone in the 33% bracket — competitive with Treasuries and high-grade corporates at certain points.

Tax-equivalent yield

Comparing taxable and tax-free yields:

Tax-Equivalent Yield = Tax-Free Yield / (1 − Marginal Tax Rate)

A 3.5% muni for someone in the 32% bracket has a tax-equivalent yield of 5.15%. If Treasuries yield 4.5%, the muni is more attractive after tax.

For lower-income investors, the calculation often favors taxable bonds. Munis make most sense for higher-bracket investors.

Credit ratings

Munis are rated by major agencies:

• AAA / Aaa — highest quality (limited number of issuers).
• AA, A — strong investment grade.
• BBB / Baa — lowest investment grade.
• Below BBB — speculative, higher risk.

Default rates have been very low for investment-grade munis historically. The 2008 crisis tested some credits; Detroit's 2013 bankruptcy and Puerto Rico's 2017 default were notable exceptions.

Insured munis

Some munis are wrapped with bond insurance. Historically, insurers like MBIA and Ambac provided AAA wrappers on lower-rated bonds. The 2008 crisis exposed insurer weaknesses; the practice has declined.

Major risks

Several worth knowing:

• Credit risk. Specific issuers can default. Detroit, Puerto Rico, several smaller cases.
• Interest-rate risk. Like all bonds, prices fall when rates rise.
• Call risk. Many munis are callable; issuers refinance when rates fall.
• Liquidity risk. Specific muni issues often trade thinly; selling can be expensive.
• AMT risk. Some munis (private-activity bonds) are subject to Alternative Minimum Tax.
• State concentration. Holding only one state's munis concentrates state-specific economic risk.

How most investors hold munis

For typical investors:

• Muni mutual funds — diversified portfolios.
• Muni ETFs — MUB (iShares National), VTEB (Vanguard), TFI (SPDR). Liquid and low-cost.
• State-specific muni funds — for residents wanting state-tax-exempt income.
• Direct ownership — for higher-wealth investors with appropriate research capacity.

Direct ownership of individual munis is more common at the higher-wealth end.

Where munis fit in a portfolio

Several considerations:

• High-tax-bracket investors in taxable accounts often benefit substantially.
• Tax-advantaged accounts (401(k)s, IRAs) — munis don't make sense; they sacrifice yield for tax benefit you don't need.
• Low-tax-bracket investors — taxable bonds usually offer better after-tax yields.
• State-resident munis offer additional state-tax savings for state residents.

What individuals should know

For typical investors:

• Compare tax-equivalent yields vs. taxable alternatives.
• Hold munis in taxable accounts, not tax-advantaged.
• Consider state-specific funds if your home state has high taxes.
• Don't over-concentrate in any single state's munis.
• Watch for callability — high-coupon bonds may be called away.

Munis are a niche but important asset class for higher-bracket US taxpayers. For most retail investors, broad bond ETFs (with some muni exposure) capture the basic yield without requiring specific muni research. For wealthier taxable investors, deliberate muni allocation can produce meaningful after-tax savings.