Yield Spread Basics

A corporate bond yielding 5% tells you nothing until you compare it to a Treasury yielding 3%; the 2% spread is what the market pays for risk.

Key takeaways

• A yield spread is the difference between a bond's yield and a reference (benchmark) yield
• Spreads compensate investors for credit risk, liquidity risk, and other non-interest-rate risks
• Wider spreads indicate higher perceived risk; tighter spreads indicate lower risk or strong demand
• Treasury yields are the typical benchmark; the spread over Treasuries is the excess yield for taking extra risk
• Tracking spreads helps you time bond purchases and assess market sentiment

The benchmark framework

When comparing bond yields, you can't look at them in isolation. A bond yielding 5% might be fantastic or mediocre depending on the context.

If Treasury bonds yield 4%, a corporate bond at 5% is offering a 1% spread (100 basis points, or "100 bps"). If Treasury bonds yield 2.5%, the same corporate at 5% is offering a 2.5% spread (250 bps). Context matters.

The benchmark is typically:

1. On-the-run Treasury (the most recently issued Treasury of similar maturity): the risk-free rate.
2. Treasury yield curve: if comparing a 5-year corporate, use the 5-year Treasury yield as the benchmark.
3. Swap rate: sometimes used instead of Treasury yields for comparisons.

The spread is:

Spread = bond yield − benchmark yield

A corporate bond yielding 4.5% when 5-year Treasuries yield 3.5% has a 1% (100 bps) spread.

What spreads compensate for

Different bonds have different risks. Treasuries are default-free (the U.S. government can print dollars). Corporate bonds carry default risk. Municipal bonds carry default risk and liquidity risk (fewer buyers than Treasuries).

The spread compensates for:

1. Credit risk: the probability the issuer defaults. A AA-rated issuer (lower default risk) trades at a tighter spread than a BB-rated issuer.
2. Liquidity risk: how easily you can sell the bond without taking a steep price. Treasuries are liquid; small corporate bonds are less so.
3. Complexity: bonds with call features, floating coupons, or exotic structures trade at wider spreads because they're harder to analyze.
4. Optionality: callable bonds (which the issuer can repay early) trade at wider spreads because the issuer has optionality.
5. Term structure: longer-maturity bonds usually trade at wider spreads to compensate for longer duration.

Spread examples across bond types (2024–2025)

These are representative; actual spreads change daily based on market conditions.

• High-grade corporate (AAA): 0.5–1.5% spread over Treasuries.
• Investment-grade corporate (BBB): 1.5–3% spread over Treasuries.
• High-yield corporate (BB and below): 3–7% spread over Treasuries (or more in credit stress).
• Municipal bonds (AAA): 0–0.5% spread (munis are sometimes valued purely on their tax-free status).
• Emerging-market sovereign bonds: 2–5% spread over Treasuries, depending on country.

A 2024 example: AGG (the bond index) held mostly AAA and AA corporates with a 1.2% spread. HYG (high-yield) held mostly BB and B corporates with a 4.5% spread. The difference is credit quality.

The credit cycle and spread changes

Spreads move as the market's view of credit risk changes.

In a benign economic environment, credit spreads tighten (narrow) because investors believe default risk is low and are willing to accept lower extra yield for taking that risk. A BBB corporate spread might fall from 2.5% to 1.8%.

In a recession or financial stress, spreads widen because investors demand higher compensation. That same BBB corporate might widen to 4% or 5% as the market fears defaults.

The 2008 financial crisis saw high-yield spreads widen to 20%+. In 2020 (COVID shock), spreads spiked then tightened quickly as the Fed intervened. Over 2023–2024, spreads remained relatively tight as credit conditions stabilized.

Option-adjusted spread (OAS)

For more complex bonds (especially those with call features or exotic structures), the simple spread (yield minus Treasury yield) isn't enough. The "option-adjusted spread" (OAS) accounts for the value of embedded options.

Example: A callable corporate bond yields 5%, and the 5-year Treasury yields 3.5%, for a simple 1.5% spread. But the issuer can call the bond if rates fall to 2% — an option worth something to the issuer. To fairly compensate the bondholder, the OAS might be 1.7%, reflecting the value of that call option.

OAS is calculated using models that assume the issuer exercises the call optimally. It's more precise than simple spread, but also harder to compute by hand. Bloomberg terminals, bond databases, and financial websites calculate OAS for you.

For most personal bond investing, simple spread (yield − Treasury yield) is sufficient. Professional managers care about OAS for exact valuations.

Using spreads to time purchases

Smart bond investors track spreads to identify opportunities.

Scenario: spreads are historically wide. If high-yield spreads are 6% and have averaged 4% over the past 10 years, you're being compensated generously for credit risk. This might be a good time to overweight corporate and high-yield bonds, expecting spreads to tighten and prices to rise as the economic cycle improves.

Scenario: spreads are historically tight. If investment-grade corporate spreads are 0.8% and have averaged 1.5%, you're being underpaid for risk. This might be a time to reduce corporate exposure and tilt toward Treasuries, expecting spreads to widen if the economy slows.

Tracking spread levels is a practical tool for rebalancing decisions. If you have a 40/60 Treasury/corporate allocation and spreads widen dramatically (credit fear), rebalancing to sell Treasuries and buy corporates at the wider spread locks in higher future returns.

Where to find spread data

• FRED (Federal Reserve Economic Data): publishes spreads for various bond categories. Look for "Corporate Yield Spread" or "High Yield Option-Adjusted Spread."
• ICE (Intercontinental Exchange): maintains spread indices for corporate and high-yield bonds.
• Bloomberg: the terminal displays spreads for individual bonds.
• Financial websites: MarketWatch, Yahoo Finance, and many brokerage platforms display spread data.
• Bond fund factsheets: Vanguard, iShares, and other fund issuers include average spreads in their fact sheets.

Spread decision tree

Spread compression and expansion

As spreads move, bond prices move inversely. When spreads tighten (narrow), bond prices rise because the same cash flows are discounted at a lower spread. When spreads widen, bond prices fall.

Example: A corporate bond with $50 annual coupons. If the spread is 2% (and Treasury yield is 3%, for a 5% total yield), the price is determined by discounting at 5%. If the spread tightens to 1.5% (total yield 4.5%), the price rises. Conversely, if the spread widens to 3%, the price falls.

Professional traders make money by betting on spread moves. For buy-and-hold investors, understanding spread moves helps you understand bond fund performance. A corporate bond fund might fall in price even if Treasury yields stayed flat, because credit spreads widened.

Summary: reading the bond market's risk appetite

Yield spreads are the market's way of pricing credit and liquidity risk. A narrow spread says, "I'm confident in credit and willing to accept low extra yield." A wide spread says, "I'm fearful and demand high compensation."

Learning to read spreads lets you:

1. Compare bonds fairly: adjust for risk when comparing a corporate to a Treasury.
2. Time the cycle: buy corporates when spreads are wide (fear, opportunity) and reduce when spreads are tight (complacency, caution).
3. Understand fund performance: when a corporate bond fund falls, check spreads — it might not be interest-rate risk, but credit-risk widening.
4. Assess value: a 2% spread on a AAA bond is too narrow; a 1.5% spread on a BB bond is too narrow. Context is everything.

Related concepts

• ./06-yield-to-maturity-ytm.md
• ./02-coupon-rate-fixed-vs-floating.md
• ./01-face-value-explained.md

Next

Spreads vary by credit quality, but they can also lead investors astray. High-coupon bonds often appear to offer great value — until you realize they're trading at a wide spread for good reason. The next article reveals the coupon bias trap: why high-coupon bonds aren't always the bargain they seem.