Investment Grade vs High Yield: Ratings, Spreads, Defaults

TL;DR. A corporate bond is “investment grade” if at least one major agency rates it BBB-/Baa3 or higher, and “high yield” (a.k.a. “junk”) if it sits a notch below. That one-notch line is a cliff: it changes who can own the bond, what the issuer pays to borrow, and how the bond behaves when the economy turns. This piece walks through what the ratings mean, how credit spreads price the difference, and how often the two groups actually default.

The rating cutoff: where investment grade ends

Three nationally recognized statistical rating organizations — Moody’s, S&P Global, and Fitch — assign letter grades that summarize an issuer’s ability to pay. The notation differs, but the cliff is identical across all three: BBB-/Baa3 is the lowest investment-grade rung; anything below is speculative grade.

The SEC’s investor education site puts it simply: a high-yield bond is one “believed to have a higher risk of default” and rated “Ba or below (by Moody’s) or BB or below (by S&P and Fitch).” That definition is the line that moves trillions of dollars in capital — pension funds, insurance companies, and many bond index funds are required (by mandate, regulation, or capital charges) to hold mostly investment grade, so falling across the line forces involuntary selling and pushes the issuer’s yield up.

Tier	Moody’s	S&P	Fitch	Classification
Highest quality	Aaa	AAA	AAA	Investment grade
Very high	Aa	AA	AA	Investment grade
Upper medium	A	A	A	Investment grade
Lower medium (the line)	Baa	BBB	BBB	Investment grade (BBB- / Baa3 = floor)
Non-investment grade	Ba	BB	BB	High yield (“junk”)
Highly speculative	B	B	B	High yield
Substantial risk	Caa	CCC	CCC	High yield (distressed)
Default imminent / occurred	Ca / C	CC / C / D	CC / C / D	Default

Source: Wikipedia: Bond credit rating, drawing on Moody’s, S&P Global, and Fitch published rating scales. The Investment-grade floor is BBB- (S&P/Fitch) or Baa3 (Moody’s).

What a credit spread actually is

The “spread” is the extra yield an investor demands to hold a corporate bond instead of a Treasury of the same maturity. It is quoted in basis points (1 bp = 0.01%). If a 10-year Treasury yields 4.50% and a 10-year BBB corporate yields 5.50%, the bond trades at a 100 bp spread.

The most commonly cited corporate-bond benchmarks are the ICE BofA US Corporate Index Option-Adjusted Spread (the IG benchmark) and the ICE BofA US High Yield Index OAS. Both are published daily by FRED. Option-adjusted spread (OAS) means the spread has been stripped of the effect of embedded options like an issuer call — so it isolates the pure credit-and-liquidity premium.

A useful intuition from the Wikipedia entry on credit spread: “if a risk-free 10-year Treasury yields 5% while junk bonds average 7%, the spread is 2%. If that spread widens to 4%… this signals the market perceives greater default risk.” Spreads are the market’s running referendum on whether issuers will pay.

Worked example: two bonds, same maturity

Imagine two 5-year corporate bonds, both with a 5.00% coupon, both issued at par ($1,000 face value), the same day a 5-year Treasury yields 4.00%:

Bond A — issuer rated A (solid investment grade). It trades at par; its yield-to-maturity equals its coupon, 5.00%. Spread = 100 bp over Treasuries.
Bond B — issuer rated B (single-B high yield). For investors to take that risk, the bond has to be cheaper. The market prices it at, say, $880, which pushes its yield-to-maturity to roughly 8.10%. Spread ≈ 410 bp over Treasuries.

Same coupon, same maturity, very different yields — because the second bond carries a meaningfully higher probability of not paying that coupon. The 310-bp gap between them is the market’s price of credit risk.

Schematic only — actual spreads vary with sector and cycle. Concept consistent with FRED ICE BofA US Corporate and High Yield OAS series.

Default risk: what history actually shows

The simplest way to see the gap between IG and HY is the realized default rate. Investment-grade defaults are rare events; speculative-grade defaults are a regular feature of the cycle.

According to the Wikipedia entry on high-yield debt, “the default rate in the high-yield sector of the U.S. bond market has averaged about 5% over the long term. During the liquidity crisis of 1989–90, the default rate was in the 5.6% to 7% range. During the COVID-19 pandemic, default rates rose to just under 9%.” Investment-grade defaults, by contrast, are typically a small fraction of a percent in any given year — almost all IG defaults happen after the bond has been downgraded to junk (see “fallen angels,” below).

The same Wikipedia source pegs US high-yield bonds outstanding at about $1.8 trillion as of Q1 2022, roughly 16% of the $10.7 trillion US corporate bond market. The remaining ~84% is investment grade — which is why pension and insurance flows so heavily dominate the IG market.

Source: Wikipedia: High-yield debt, citing long-term and crisis-period US speculative-grade default rates.

Recovery: what bondholders get back when an issuer defaults

Default is not zero. When a company defaults, bondholders receive a recovery — the present value of whatever they ultimately get from restructuring or liquidation. Seniority in the capital structure drives the number.

The Basel II foundation internal-ratings-based approach hard-codes regulatory recovery assumptions that are widely used as reference points: senior unsecured claims on corporates carry a 45% loss-given-default (so a 55% recovery), and all subordinated claims carry a 75% LGD (so a 25% recovery). Senior secured claims with eligible collateral can recover more. Empirical recovery rates fluctuate by cycle and sector, but the seniority hierarchy holds: senior secured > senior unsecured > subordinated > preferred equity.

For a high-yield investor, expected loss is roughly probability of default × loss given default. A bond with a 6% one-year default probability and a 60% LGD has ~3.6 percentage points of expected annual credit loss — which the spread has to more than cover for the trade to be worth it.

When the line breaks down: fallen angels, rising stars, the BBB cliff

The IG/HY line is not a static one. Issuers move:

Fallen angels — bonds originally issued investment grade that get downgraded to junk. Ford and GM were textbook fallen angels in 2005 when both were cut to junk status. Because so many investment-grade portfolios are forced sellers when a name crosses the line, fallen-angel debt often trades at temporary discounts before settling into the HY market.
Rising stars — junk-rated issuers that improve enough to be upgraded back to investment grade. Spreads tighten in anticipation if the market sees the upgrade coming.
The BBB cliff — the bulk of IG bonds outstanding are rated in the BBB tier (the lowest IG notch). A single-notch downgrade pushes them off the cliff into HY. In a recession, this risk gets priced even into BBB names that have not yet been downgraded.

Common mistakes

“Investment grade can’t default.” Wrong. IG defaults are rare, but they happen — most famously when investment-grade issuers fail abruptly enough that the rating cannot keep up with the deterioration. The right frame: IG is low default risk, not no default risk.
Confusing yield with return. A 9% yield-to-maturity on a single-B bond is not a 9% expected return. Subtract expected credit losses (default rate × loss given default) to get a more honest number.
Ignoring duration. A 30-year investment-grade bond can lose more on a 100 bp rate move than a 5-year high-yield bond would lose if its spread widened by the same amount. Credit risk and rate risk are separate axes — see Bond Duration & Convexity.
Treating “the high-yield index” as one thing. The single-B and CCC segments behave very differently in a downturn: CCC blows out first, single-B follows, BB is closer to BBB. The index average hides that.

Related concepts and what to learn next

If this clarified the rating cliff, the natural next stops are duration and convexity (how bond prices move with rates), CLOs (the dominant buyer of leveraged loans, the loan-market cousin of HY), and private credit vs syndicated loans (the non-public corner of the credit universe).

Sources

Disclosure: This article was produced with AI assistance and reviewed before publication. It is for informational purposes only and is not investment advice.