Valuing Callable Municipal Bonds
A municipal bond’s embedded call option allows the issuer of the bond to “call” (i.e., pay back) the debt at a date prior to the bond’s final maturity. This, in turn, potentially allows the issuer to reduce the cost of financing when interest rates decline – in the same manner that a homeowner might refinance a mortgage.
To compensate investors, bonds with embedded call options, known as callable bonds, are typically offered at higher yields than non-callable bonds. Callable bonds represent the majority of the municipal bond market. In fact, historically, on average roughly 83% of all municipal bonds issued over the past 10 years have featured call options.1 When compared to taxable fixed income benchmarks, the tax-exempt market is more heavily weighted toward callable bonds as a result (figure 1). This structural difference needs to be considered when investing in tax-exempts given the difference between maturity matched and duration matched curves (figure 2).
Figure 1
As of 31 May 2025
Source: Bloomberg, PIMCO
Figure 2
As of 30 June 2025
Source: Thomson Reuters, Bloomberg
Taxable equivalent yield calculated using a federal tax rate of 37% with a Medicare tax rate of 3.8% to apply an aggregate tax rate of 40.8%. AAA MMD Muni and Taxable-Equivalent AAA MMD Muni are a proxy for the Thompson Reuters AAA Muni curve. Treasury is a proxy for the US Treasury Curve.
This creates complications for muni investors since pricing callable bonds can be a tricky proposition. This can create opportunities for savvy bond managers and investors who can take advantage of market inefficiencies to potentially generate additional yield.
Understanding the MMD yield curve and pricing newly issued municipal bonds
The municipal market data (MMD) yield curve is the most widely referenced yield curve in the municipal bond market. For investors familiar with the U.S. Treasury yield curve, which quotes the yield to maturity (YTM) on non-callable Treasury bonds, the conventions of the MMD curve might seem unorthodox.
The benchmark bonds along the MMD curve reflect the standard for newly issued bonds in the municipal market, with some base assumptions:
- By convention, bonds carry a 5% coupon, although this can change.
- Bond maturities less than or equal to 10 years are non-callable.
- Maturities greater than 10 years have a 10-year lockout period, which means they are not callable for the first 10 years.
- Yield to maturity (YTM) is used for non-callable structures, while yield to call (YTC) is used for callable structures.
Given these assumptions, the MMD curve acts as a benchmark for determining how cheap or expensive a newly issued 5% coupon callable municipal bond (or non-callable bond under 10 years to maturity) appears relative to the broader market.
Pricing munis in the secondary market is more challenging
However, most bonds in the secondary market do not match the call and coupon assumptions of the MMD curve, which has led to the development of a municipal market convention of quoting yield spreads on a maturity-matched basis. Unfortunately for investors, this can lead to bond mispricing.
Let’s take, for example, a bond with 15 years to maturity and a seven-year lockout period (abbreviated as 15NC7). Because this bond’s first call date is in seven years, it has no direct comparison point on the MMD curve. (Recall that the MMD curve assumes the bond is not callable for 10 years.)
To adjust for this, a conventional market-spread pricing approach would match the 15NC7 with a 15-year maturity point on the MMD – in this case, a 15NC10 – and use the corresponding yield spread to quote the bond’s price.
Note that although the two bonds have very different structures (a 7-year first call versus a 10-year first call), they are priced as if they’re structured the same. The spread on the 15NC7 is calculated as the difference between its YTC and the 15NC10 MMD yield, which may or may not represent a true measure of its value, depending on the market environment. This may reflect either too much or too little value, since the bond is not being compared to a bond with the same structure.
Fortunately, we believe there’s a more accurate way to price municipal bonds.
Using daily MMD yield and volatility measures, it is possible to calculate the MMD-implied yields on bonds of all call and coupon combinations using an interest rate and pricing approach. The resulting yield spread should provide a more accurate measure of the value of the bond.
Positioning municipal investors to benefit from opportunities in callable bonds
Working with a municipal bond manager with strong quantitative research capabilities and expertise in sourcing and valuing callable bonds may allow investors to harvest municipal bond market inefficiencies and generate additional yield.
Learn more about municipal bond markets and PIMCO’s investment ideas at pimco.com/munis.
1 Source: SIFMA U.S. municipal bond issuance data as of 3 June 2024. 10-year period reflects 1 January 2013 through 31 December 2023.↩
Disclosures
Unless stated otherwise, information contained herein is as of 31 May 2025. The information may be stale and should not be relied upon.
Past performance is not a guarantee or a reliable indicator of future results.
All investments contain risk and may lose value. Investing in the bond market is subject to risks, including market, interest rate, issuer, credit, inflation risk, and liquidity risk. The value of most bonds and bond strategies are impacted by changes in interest rates. Bonds and bond strategies with longer durations tend to be more sensitive and volatile than those with shorter durations; bond prices generally fall as interest rates rise, and low interest rate environments increase this risk. Reductions in bond counterparty capacity may contribute to decreased market liquidity and increased price volatility. Bond investments may be worth more or less than the original cost when redeemed. Income from municipal bonds is exempt from federal income tax and may be subject to state and local taxes and at times the alternative minimum tax; a strategy concentrating in a single or limited number of states is subject to greater risk of adverse economic conditions and regulatory changes.
There is no guarantee that these investment strategies will work under all market conditions or are suitable for all investors and each investor should evaluate their ability to invest long-term, especially during periods of downturn in the market. No representation is being made that any account, investment product, or strategy will or is likely to achieve profits, losses, or results similar to those shown. Investors should consult their investment professional prior to making an investment decision.
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