iShares Long-Term National Muni Bond ETF (LMUB)

LMUB — key facts

Aspect	Detail
What it holds	Long-maturity U.S. municipal bonds from states and cities
Maturity range	Typically 15–30+ years; average maturity varies
Bond types	General obligation, revenue bonds, taxable municipals
Tax treatment	Interest is exempt from federal income tax; often exempt from state and local taxes for in-state residents
Expense ratio	Very low — among the cheapest muni bond funds
Primary risk	Credit risk (issuer default) and duration risk (price sensitivity to interest-rate changes)
Appropriate for	High-income individuals in high tax brackets seeking tax-exempt fixed income

Municipal bonds are debt securities issued by U.S. states, cities, counties, school districts, and other local authorities to finance infrastructure, schools, and public services. Unlike U.S. Treasury or corporate bonds, the interest income from municipal bonds is exempt from federal income tax — and, if you live in the state that issued the bond, often exempt from state and local income taxes as well. LMUB pools that tax advantage by holding a diversified portfolio of long-maturity municipal bonds from across the country.

The attraction of municipal bonds is tax efficiency. A taxable bond paying 5% is not equivalent to a municipal bond paying 3.5%, if you are in a high federal tax bracket. After paying federal and possibly state taxes on the taxable bond’s interest, your after-tax yield may fall to 3% or below. The municipal bond’s 3.5% yield is yours free and clear. For wealthy individuals in high tax brackets, especially residents of high-tax states, municipal bonds can offer superior after-tax returns compared to treasuries or corporate bonds.

LMUB’s focus on long-term bonds — the 15–30+ year end of the maturity spectrum — means the fund has substantial interest-rate sensitivity, or duration. When interest rates fall, the fund’s price rises sharply because the fixed coupons those bonds pay become more valuable. Conversely, when rates rise, the fund’s price falls. This duration risk is the trade-off for collecting higher yields at the long end of the municipal curve. Someone buying LMUB is accepting that fluctuation in exchange for earning more interest than they would from short-term munis.

The portfolio typically includes both general obligation bonds — backed by the full taxing authority of a state or city — and revenue bonds, which are secured by specific revenue streams (highway tolls, water utilities, hospital operating revenues). The issuer diversity is broad: holdings span dozens of states, dozens of major cities, water utilities, airport authorities, and other entities. This diversification protects against concentrated credit losses, though municipal defaults, while rare, do happen. Puerto Rico, several cities, and smaller entities have defaulted or restructured debt in recent decades.

LMUB’s expense ratio is among the lowest in the muni bond space, because municipal bonds are relatively liquid and straightforward to trade, and the strategy requires no special analysis. The fund rebalances periodically to maintain its target maturity range but is not actively trading in and out. This low-cost structure means a larger share of the fund’s yield flows through to investors.

The yield the fund distributes depends on prevailing interest rates and market conditions. When rates are elevated and the market fears recession, muni yields can spike and LMUB’s yield becomes more attractive. When rates are falling and credit conditions are easy, muni yields compress and LMUB yields less. The fund’s income is distributed monthly or quarterly, and can be reinvested to compound gains or withdrawn as needed.

One structural feature worth understanding: municipal bond funds distribute tax-exempt interest but can also generate capital gains if they sell bonds at a profit (if rates have fallen since purchase) or incur capital losses (if rates have risen). The capital gains component is subject to tax, whereas the interest component is tax-exempt. For this reason, investors in high tax brackets should pay attention to the fund’s turnover and any capital gains distributions.

The credit risk in LMUB is real. The fund holds IOUs from states and cities, and while default rates are low relative to corporate bonds, they are non-zero. State and local budgets can be stressed by recessions, demographic decline, or mismanagement. General obligation bonds backed by taxing authority are safer; revenue bonds secured by specific income streams carry more risk if those revenues decline (as airport bonds learned during the pandemic). LMUB’s diversification across issuers mitigates single-issuer risk, but it does not eliminate credit risk entirely.

LMUB is best suited for investors in high federal income tax brackets — typically those in the highest marginal rates — who want to diversify their fixed-income holdings beyond Treasuries and corporates. It is also sensible for state residents seeking in-state municipal bonds, where the additional state and local tax exemption compounds the federal benefit. Someone in a lower tax bracket — or living in a state with no income tax — is likely better off owning taxable bonds, which offer higher pretax yields that more than compensate for the tax liability.

Research should begin with the fund’s prospectus and current factsheet, which disclose the breakdown of holdings by state, issuer, and bond type, as well as the weighted-average maturity and the overall credit rating distribution. Review the fund’s recent yield and any capital gains distributions. Compare the after-tax yield of LMUB to equivalent taxable alternatives (Treasuries, corporate bonds, other muni funds) given your own tax bracket — calculators on financial websites make this straightforward. Finally, understand the current interest-rate environment and whether long-maturity bonds seem attractively priced relative to short-maturity munis, and whether state and local credit conditions are stable or deteriorating.