This is a passive ETF that tracks a US municipal bond index of bonds with maturities of one year or more, excluding bonds subject to the alternative minimum tax (AMT). It covers the major municipal bond segments, including general obligation bonds, revenue bonds, pre-refunded bonds, and insured bonds, on a market-capitalization-weighted basis.

It seeks federally tax-exempt interest income and suits investors with high taxable income who want intermediate- to long-term bond diversification.

Launched in 2007 by State Street (SSGA), the ETF is managed passively (index tracking).

Rather than buying every security in the index directly, the fund uses a sampling approach to replicate similar risk and return characteristics. Because individual municipal bonds have low liquidity, sampling is generally considered a more efficient method than full replication.

• The AMT-excluded structure improves after-tax returns for high-income investors
• Covers all municipal bond segments, including general obligation bonds, revenue bonds, and pre-refunded bonds

Assets under management (AUM) stand at $3.0B, and the total expense ratio is 0.23% per year.

Its fees are somewhat higher than those of comparable ETFs such as MUB and VTEB, but it offers a long track record and stable liquidity under State Street (SSGA) management.

Price volatility in the US municipal bond market varies with the level of interest rates. When expectations of rate cuts rise, prices tend to recover, whereas in a rising-rate environment the fund's intermediate- to long-term duration can put downward pressure on prices.

Tax-saving demand from investors facing heavy tax burdens is a steady driver of inflows into municipal bond ETFs. Fund flows tend to become more active during year-end tax planning season or when tax rate changes are under discussion.

Its strengths are federally tax-exempt interest income and broad diversification, while its weaknesses are interest rate sensitivity and relatively low liquidity.

MUB, shown in the table, is a comparable municipal bond ETF managed by iShares with lower fees, and VTEB is Vanguard's low-fee municipal bond ETF. CGMU and JMUB are relatively newly launched municipal bond ETFs that differ in issuer and strategy. CMF focuses on California municipal bonds and is a specialized product aimed at capturing the state tax exemption for California residents. Investors who want municipal bond exposure with shorter duration can also consider SHM, a short-term municipal bond ETF.

Before investing in TFI, it is important to review the tax structure, the interest rate environment, and your holding period thoroughly. The practical benefit of the federal tax exemption varies greatly depending on your taxable income bracket.

In a rising-rate phase, the fund's intermediate- to long-term duration can increase downward price pressure. In addition, it can be exposed to credit risk if the finances of a particular local government deteriorate, so monitoring credit ratings is necessary.

This is an ETF to consider when an investor with high taxable income wants diversified municipal bond exposure for federally tax-exempt interest income. If cost is the priority, MUB and VTEB can be alternatives, and for shorter duration, SHM can be an alternative.