Credit Spreads Explained: Investment Grade vs High Yield and What Widening Signals
A credit spread is the extra yield a company pays to borrow compared with the US government for the same length of time. If a five-year Treasury yields 4 percent and a company’s five-year bond yields 5.5 percent, the spread is 1.5 percentage points, or 150 basis points (one basis point is 0.01 point). That gap is the market’s price for the chance the company won’t pay back, plus a bit for being harder to sell than a Treasury. Spreads move every day, and they move before most other signs of trouble. When companies get into difficulty, bond investors usually notice first, and that makes spreads one of the best real-time stress gauges in finance.
How spreads are measured: OAS
The standard measure is the option-adjusted spread, or OAS. Many corporate bonds can be called (repaid early) by the issuer, which is worth something to the company and costs the bondholder. A plain yield spread mixes that option value in with credit risk. OAS strips it out by modelling the bond’s cash flows across many interest-rate paths, which leaves the part of the spread that pays for credit and liquidity. It is measured against the whole Treasury curve, so a seven-year bond is compared with seven-year Treasury rates rather than a single benchmark.
The most widely followed series are the ICE BofA indexes, published daily:
- ICE BofA US Corporate Index OAS covers investment-grade bonds (rated BBB- or higher) with at least $250 million outstanding and more than a year to maturity.
- ICE BofA US High Yield Index OAS covers bonds rated below investment grade, often called junk.
Bloomberg runs competing indexes, and the numbers differ slightly. They tell the same story. One practical note: since April 2026, the St. Louis Fed’s free FRED database shows only the latest three years of these ICE series, so long-run history now has to come from ICE or a terminal.
Investment grade vs high yield
The split follows the credit rating scale. Bonds rated BBB- or Baa3 and above are investment grade (IG); anything lower is high yield (HY). Our guide to credit rating scales shows how S&P, Moody’s and Fitch line up and how default rates jump below the cutoff. That jump is why the two markets behave like different asset classes.
| Investment grade | High yield | |
|---|---|---|
| Ratings | AAA to BBB- | BB+ and below |
| Typical issuers | Apple, utilities, big banks, hyperscalers | Private-equity-owned companies, smaller cable, energy and retail firms |
| What drives the spread | Interest rates, supply, broad risk appetite | Default risk, recovery values, the economy |
| Long-run average OAS (1997 to 2025) | About 1.9 points (median about 1.7) | About 5.2 points (median about 4.6) |
| “Normal” range | Roughly 1.0 to 2.5 points | Roughly 3 to 8 points |
| Early October 2026 | About 0.85 points | About 3.1 points |
About half of the IG market by value is now rated BBB, the lowest rung, compared with about a quarter in the late 1990s. That matters in a downturn. A BBB company cut to BB becomes a “fallen angel”, and many insurance companies and IG-only funds have to sell it, so a wave of downgrades can push big volumes of debt into a high-yield market that has trouble absorbing it.
High-yield debt also comes with its own structures. Toggle notes and payment-in-kind (PIK) loans let a struggling borrower pay interest with more debt instead of cash, and a rise in PIK use is often an early sign of strain.
Where spreads have been: crisis peaks and tights
Spreads spend long stretches tight and then gap wider in a hurry. These are the landmark readings on the ICE BofA indexes:
| Episode | High-yield OAS | Investment-grade context |
|---|---|---|
| Mid-2007, pre-crisis low | About 2.4 points, the tightest on record | Very tight |
| Mid-December 2008, after Lehman | Roughly 20 points, the widest on record | BBB spreads above 6 points |
| 2015 to 2016 oil crash | About 8.9 points | Moderate widening |
| March 23, 2020, Covid shock | 10.87 points | BBB spreads around 4 points or more |
| April 7, 2025, tariff shock | 4.61 points | IG at 1.20 points |
| 2026 lows | 2.60 points (August 28) | IG at 0.73 points (January) |
Two things stand out. In 2008 high-yield spreads stayed above 10 points for months, because defaults were real and the banking system was broken. In 2020 they more than doubled in about a month and then gave back a large part of the move within weeks, once the Federal Reserve announced it would buy corporate bonds, a first. The fastest widening is not always the deepest one.
The April 2025 tariff episode is a useful template for a modern scare: high-yield spreads jumped to 4.61 points within days of the tariff announcement, then retraced most of that over the following months as the worst tariff threats were paused.
What widening signals, and what it doesn’t
A wider spread means investors want more compensation to lend to companies. The reasons differ, and the pattern of widening tells you which one is in play.
- HY widens a lot, IG barely moves. The market is worried about weak borrowers specifically: default risk, refinancing walls, a sector in trouble. This is the classic early-slowdown pattern.
- Both widen together, sharply. A broad risk-off move or a liquidity squeeze, often alongside a spike in the VIX. Funds sell what they can, not what they want to.
- CCC widens while BB holds. Trouble is concentrated in the weakest tier. Those names usually default first.
- IG widens on heavy issuance. Supply alone can push spreads out when big borrowers flood the market, which says less about credit quality.
Spreads have tended to widen before and during recessions, and HY spreads above roughly 5 to 6 points have historically lined up with recessionary conditions. They are a better confirming signal than a long-range forecaster. They compare well with the yield curve, which gives early but unreliable warnings; spreads give later warnings that are rarely false. Very tight spreads have their own message: lenders are being paid little for the risk they take, so there’s not much cushion if things go wrong. Late-cycle tights, such as mid-2007, have come before some of the worst periods for credit. Equity sentiment gauges like the CNN Fear & Greed Index include a junk bond demand component for this reason.
Where things stand in October 2026
After a long squeeze lower, spreads have started to move. The high-yield OAS touched 2.60 points on August 28, 2026, among the tightest readings since 2007. By October 1 it was 3.24 points before easing to 3.10, a widening of more than half a point in about a month. Investment-grade spreads, which were as tight as 0.73 points in January 2026, have drifted out to about 0.85.
The causes being cited are mostly about supply and rates, not defaults. September brought heavy junk issuance, and investors are digesting huge borrowing tied to AI data centers, with hyperscalers increasingly funding capex through bond sales. The pressure has been sharpest in the lowest-rated bonds. Higher Treasury yields add to it: the 10-year is above 5 percent and the Fed raised rates in September 2026, which lifts the all-in cost of borrowing even where spreads hold. This page reflects conditions as of early October 2026.
Private credit: the part spreads don’t show
A growing share of riskier corporate lending never touches the public bond market. Private credit funds lend directly to mid-sized and private-equity-owned companies, mostly with floating-rate loans held to maturity, and the market had grown to roughly $2 trillion globally by 2023. Those loans aren’t priced daily. Funds mark them to models every quarter, so a deterioration that would show up overnight in a public HY spread can take months to appear, or appear only when a borrower fails.
That makes public spreads an incomplete picture. Watch for signs in the private market directly: rising PIK interest, more covenant amendments, falling share prices of listed business development companies (BDCs, the public vehicles that hold private loans), and sudden collapses like auto-parts maker First Brands and subprime auto lender Tricolor in September 2025, where lenders discovered problems late. When an auditor attaches a going concern opinion to a leveraged borrower’s accounts, it is often the first public sign of trouble that private lenders have known about for a while.
What to watch
- HY OAS level and speed. A move from 3 to 4 points in a few weeks matters more than a slow drift. Above 5 to 6 points, markets are pricing a real slowdown.
- The HY minus IG gap. A widening gap means the market is separating weak borrowers from strong ones.
- CCC spreads. The first place defaults show up.
- New-issue concessions. How much extra yield new deals need over existing bonds tells you how hungry buyers are.
- Fallen angel volumes and PIK usage. Early signs of downgrade waves and cash-strapped borrowers.
- Bank lending standards. The Fed’s quarterly survey of loan officers tends to move with spreads.
For definitions of the terms used here, the Referently glossary of financial markets covers OAS, basis points and the rest. The practical rule: a slow drift in spreads is mostly noise about supply and rates. A fast move in high yield, led by the weakest borrowers and not reversed within weeks, is the credit market telling you something the stock market may not have priced yet.