TL;DR
- Credit spreads measure how much extra yield investors demand to hold corporate bonds instead of "risk-free" Treasuries — the wider the spread, the more fear in the market
- HY OAS (High Yield Option-Adjusted Spread) tracks junk bond risk premiums and tends to lead equity selloffs by days to weeks
- IG OAS (Investment Grade Option-Adjusted Spread) moves more slowly but signals deeper structural stress when it widens meaningfully
- When spreads widen while stocks hold steady, the bond market is usually right — and equities are usually wrong
What Is a Credit Spread — The Simple Version
Think of the bond market as a lending bar. The U.S. government walks in and gets the best rate in the house — it's the most reliable borrower on earth, so lenders charge it almost nothing extra. Now a company walks in. Depending on how shaky its finances look, the bar charges it more. A solid blue-chip company pays a little more than the government. A heavily indebted company with spotty earnings pays a lot more.
That premium — the extra interest rate above what the Treasury pays — is the credit spread.
More precisely: a credit spread is the difference in yield between a corporate bond and a comparable Treasury bond of the same maturity. If a 10-year Treasury yields 4.5% and a corporate bond yields 6.0%, the spread is 150 basis points (1.50%).
The "option-adjusted" part of OAS accounts for embedded options in bonds — like a company's right to call the bond early. Stripping those out gives you a cleaner read on pure credit risk. For most practical purposes, when you're watching OAS as a market signal, the "option-adjusted" mechanics are in the background. What matters is the direction and magnitude of the spread.
Two spreads dominate macro analysis:
- HY OAS — High Yield Option-Adjusted Spread. Tracks bonds rated BB and below. These are companies with meaningful default risk. Think leveraged buyouts, distressed balance sheets, cyclical businesses running hot.
- IG OAS — Investment Grade Option-Adjusted Spread. Tracks bonds rated BBB and above. These are the Apples and JPMorgans of the world — not risk-free, but close enough that the spread moves are subtle and meaningful when they happen.
Why Credit Spreads Matter for Investors
Here's the thing about equity investors: they tend to watch other equity investors. Credit investors watch something different — they watch cash flows, debt coverage ratios, default probabilities. They're the skeptics at the table, and they get paid to be paranoid.
When credit spreads widen, it means bond investors are demanding more compensation to hold corporate debt. That's fear pricing in. And because credit investors are often earlier to stress than equity investors — they see the same companies from the debt side, where the math on survival is more binary — spread widening tends to precede equity weakness.
This isn't theoretical. During the COVID crash in February-March 2020, HY OAS blew out from roughly 300 basis points to over 1,100 basis points in about six weeks. Equities followed the credit market down, not the other way around. In the 2022 rate-hiking cycle, IG OAS began widening in January 2022 — the same month the S&P 500 peaked before its 25% drawdown.
The relationship isn't perfectly timed, and it's not a magic trigger. But the pattern is consistent: credit leads, equities follow.
The practical implication: if you're watching $SPY or $QQQ and trying to assess whether a selloff has real structural legs or is just noise, check the credit spreads. A stock market dip with tight spreads is usually a dip to buy. A stock market dip with widening spreads is a warning that the bond market smells something the equity crowd hasn't priced yet.
How Credit Spreads Work — The Details
Credit spreads are quoted in basis points (bps), where 100 bps equals 1 percentage point. Here's a rough historical context for reading the numbers:
HY OAS historical ranges:
- Below 300 bps: Tight. Risk appetite is high. Investors are comfortable taking on junk bond exposure.
- 300–500 bps: Normal range. Some caution, but not stress.
- 500–700 bps: Elevated. Recession risk is being priced.
- Above 700 bps: Stress territory. Historically associated with recessions or acute financial dislocations.
- 2020 peak: ~1,100 bps. 2008-2009 peak: ~2,000 bps.
IG OAS historical ranges:
- Below 100 bps: Tight. Investment grade credit is well-bid.
- 100–150 bps: Normal.
- 150–200 bps: Elevated. Worth watching.
- Above 200 bps: Stress. Historically rare outside recessions.
The mechanics work like this: when economic conditions deteriorate — or when investors expect them to — the perceived probability of corporate defaults rises. To compensate for that risk, buyers of corporate bonds demand higher yields. Since Treasury yields are anchored by monetary policy expectations, the spread between corporate yields and Treasury yields widens.
This dynamic is self-reinforcing. Wider spreads mean higher borrowing costs for companies. Higher borrowing costs squeeze margins and reduce the ability to refinance debt. That increases actual default risk, which widens spreads further. In a stress scenario, this feedback loop accelerates fast — which is why HY OAS can move from 350 to 700 bps in a matter of weeks.
The divergence between HY and IG is also informative. When HY widens but IG stays tight, the stress is concentrated in lower-quality credit — a warning sign, but not yet systemic. When IG starts widening alongside HY, institutional investors are getting defensive. That's a different signal — it means the concern has moved up the credit quality ladder, and the stress is broader than just overleveraged companies.
One more mechanic worth understanding: the relationship between credit spreads and the equity risk premium. Both measure the same underlying thing — how much extra return investors demand for taking risk above the risk-free rate. When HY OAS and equity volatility (like the VIX) diverge sharply, one of them is mispriced. Historically, the credit market is the more reliable signal.
How to Use This in Your Investing
You don't need to trade corporate bonds to use credit spreads. They're a diagnostic tool — a check on whether the equity market's confidence is warranted.
Here's a practical framework:
When spreads are tight and compressing: Risk appetite is healthy. The bond market isn't pricing stress. Equity dips in this environment tend to be shallower and recover faster. Not the time to be aggressively defensive.
When spreads are stable but elevated: The bond market has already priced some risk. Watch for whether spreads stabilize or continue widening. Stabilization often precedes equity recovery.
When spreads are widening rapidly: This is the signal that matters most. Especially watch for HY OAS breaking above its 200-day moving average or crossing key historical thresholds (400 bps, 500 bps). When IG OAS starts moving in the same direction, the concern is systemic.
The divergence trade: If $SPY is holding near highs but HY OAS is quietly grinding wider, that's a setup worth watching. The equity market is telling one story; the credit market is telling another. Historically, the credit market wins that argument.
You can track credit spread data alongside the liquidity picture on AC's AC Signal — where net liquidity, Fed balance sheet data, and risk indicators are updated regularly. Watching spreads in the context of net liquidity is the full picture: tight spreads plus rising liquidity is the most bullish macro setup. Widening spreads plus draining liquidity is the most dangerous combination.
The S&P 500 was trading around 6,591 on March 25, 2026, with net liquidity at $5.78T. Watching whether credit spreads confirm or contradict that equity level is exactly the kind of cross-asset check that separates macro-aware investing from just watching price action.
FAQ
Q: What's the difference between HY OAS and IG OAS? A: HY OAS tracks high-yield (junk) bonds — companies with below-investment-grade credit ratings and meaningful default risk. IG OAS tracks investment-grade bonds from more financially stable companies. HY OAS is more volatile and tends to move earlier in a risk-off cycle; IG OAS moving significantly is a sign the stress has become more systemic.
Q: Where can I find current HY OAS and IG OAS data? A: The Federal Reserve Bank of St. Louis (FRED) publishes both series for free — search for "ICE BofA US High Yield Option Adjusted Spread" and "ICE BofA US Corporate Option Adjusted Spread." Both are updated daily. You can also track them in context with other macro signals on AC Signal.
Q: Do credit spreads always predict stock market crashes? A: No — and that's an important caveat. Credit spreads are a risk signal, not a crystal ball. They can widen without a full equity crash following, particularly if the Fed intervenes quickly or if the stress is contained to a specific sector. What they reliably signal is that the bond market is pricing elevated risk. Whether equities follow depends on how the underlying stress resolves.
Q: What level of HY OAS should I start paying attention to? A: Watch for HY OAS crossing above 400–450 bps — that's where historical data suggests the bond market is pricing meaningful recession risk. Above 500 bps, the signal gets louder. The absolute level matters less than the direction and velocity: a spread moving from 300 to 400 bps in two weeks is more concerning than one sitting at 420 bps for six months.
Q: Can credit spreads be too tight — a warning sign in the other direction? A: Yes. Extremely tight spreads (HY OAS below 250 bps, IG OAS below 75 bps) signal that investors are pricing near-zero default risk — which is almost never accurate. When spreads compress to historical extremes, it often means the market is complacent and credit risk is being underpriced. That's not an immediate sell signal, but it's a sign that the margin of safety in risk assets is thin.