Why is one notch on the scale worth more than all the others?
Somewhere in the middle of the ratings scale there is a line. Above it, bonds are investment grade. Below it, they are high yield — also called speculative grade, sub-investment grade, or, in older market slang, junk.
The line falls between the lowest notch of the triple-B category and the highest notch of the double-B category. In terms of credit opinion, that is one notch: a marginal change in a marginal judgement. In terms of market consequences, it is the largest step on the entire scale.
Why a convention has such force
The boundary matters because it has been written into things:
- Investment mandates. Many funds, insurers and pension portfolios are permitted to hold investment-grade bonds only. Not "prefer" — permitted.
- Index membership. Investment-grade and high-yield bond indices are separate universes with separate rules, and vast sums track them.
- Regulatory and capital treatment. Several regimes have applied different capital charges or eligibility rules across the line.
- Collateral eligibility. What can be posted, pledged or repo'd often depends on which side of the line a bond sits.
The result is a discontinuity in the buyer base, not just in the risk. Cross the line downward and a large set of holders becomes unable to hold the bond, while the pool of eligible buyers is smaller and prices differently.
Illustrative spread levels
Rounded and illustrative, to show shape rather than a market level:
- Around the triple-B area: 140bp
- Around the double-B area: 280bp
- Around the single-B area: 450bp
- Below that: 900bp and up, with much wider dispersion
The jump across the boundary is large for what is, in credit-opinion terms, a single notch — partly because default risk really does accelerate, and partly because of the plumbing above. It is not the widest step in basis-point terms: the numbers above put double-B to single-B at 170bp against 140bp across the line. What makes the boundary different is not the size of the step but who is allowed to stand on each side of it.
Fallen angels and rising stars
A bond downgraded from investment grade to high yield is a fallen angel. A high-yield issuer upgraded across the line is a rising star.
A fallen angel event is mechanical as much as fundamental. Index funds tracking an investment-grade benchmark must sell, on a schedule the index rules define. Mandate-constrained holders must sell. The buyers are a different, smaller set of investors, who price the bond on high-yield conventions — spread to worst, different covenant expectations, different liquidity assumptions.
Split ratings
Agencies frequently disagree, so a bond can be investment grade to one and high yield to another. Index providers resolve this with published rules — some take the middle rating of three, some the lower of two, some an average. The bond's classification is therefore partly a function of whose rulebook you are reading, which is a useful reminder that "investment grade" is a defined term, not a natural category.
The honest framing
Everything above describes market plumbing. It is not a statement that one side of the line is a better place to be. Investment grade is not safe and high yield is not doomed; they are different risk-and-compensation profiles serving different roles, and both experience good and bad periods. What the line reliably does is change who can own the bond — and that alone reshapes its price.
In the data
The New York Fed's Corporate Bond Market Distress Index does not publish one distress number, it publishes three for the same week: the whole market, investment grade and high yield. The newest week is below.
The split exists because the two sides of the boundary behave differently enough that one index cannot describe both. On 19 June 2026 investment grade read 0.23 against high yield's 0.06: three separate constructions, each measured against its own history, not three slices of one scale.
Try it now
Look at the boundary:
- The newest week is in the section above; eight weeks of early 2020 are below. If the numbers sat on one scale of credit risk, high yield could never read calmer than investment grade. Find the weeks where it does, and the week in 2020 where the ordering flips.
- Now the same boundary in prices. Below are five years of a broad investment-grade bond fund and of a high-yield fund. Track the gap between them across a stressed stretch: does it widen more than either line does on its own?
- Note one structural reason for that behaviour from this lesson. You are now reading market plumbing, not just credit quality.