Split Credit Ratings Explained

A split credit rating happens when two or more of the major rating agencies—Moody’s, Standard & Poor’s (S&P), and Fitch—assign different ratings to the same bond or issuer, creating ambiguity about creditworthiness and complicating investment decisions and index inclusion.

Why Rating Agencies Disagree

The three major agencies—Moody’s, S&P, and Fitch—use similar frameworks but apply them differently. Each has its own rating committee, team of analysts, and proprietary analytical models. They don’t always reach the same conclusion.

An issuer’s ability to pay its debts isn’t a binary fact; it involves judgment about management quality, competitive position, economic sensitivity, and tail-risk scenarios. Agency A might focus on the company’s strong operating cash flow and assume a moderate recession scenario. Agency B might emphasize rising leverage and assume a more severe downturn. Both are reasonable, but they lead to different ratings.

Timing also matters. If a company announces bad news, one agency might downgrade immediately while another waits for more data. By the time the second agency moves, the downgrade is no longer a surprise to the market, but it’s now official, and the split has widened temporarily.

Information sets can differ too. An agency with deeper relationships or research might know about pending operational changes before others. Geographic or sector expertise can also vary—an agency with a large Asian team might have a keener eye for emerging-market credit risks than competitors.

How Splits are Classified

A one-notch split is when ratings differ by a single grade step—say, Moody’s A3 versus S&P A-. Both are within the same broad category (A territory), and the difference is often considered minor.

A two-notch split is more material—perhaps BBB versus BB, straddling the investment-grade/non-investment-grade boundary. This split is economically meaningful because it implies disagreement on whether the issuer is truly creditworthy or risky.

A wide split (three or more notches) is rare and usually a red flag. It suggests agencies have materially different views of risk, often because new information has prompted one agency to move faster than others, or because they disagree fundamentally on the company’s prospects.

The Investment-Grade Boundary Problem

The dividing line between investment-grade (BBB and above) and junk bond (BB and below) is economically significant. Many institutional investors—mutual funds, pension funds, insurance companies—have mandates requiring them to hold only investment-grade bonds. A split straddling this boundary creates real friction.

If Moody’s rates an issuer BBB (investment-grade) and S&P rates it BB (non-investment-grade), which is correct? Index managers and fund committees have developed protocols. Some funds use the most conservative rule: if any agency rates the security as non-investment-grade, they treat it as such. Others require a majority of agencies to agree, or they use a blended approach.

This threshold effect means a split at the boundary can be more disruptive than a two-notch split entirely within investment-grade. An issuer rated BBB by Moody’s and BB by S&P might be excluded from broad bond ETFs that demand investment-grade status, depressing its price and yield.

Market Reaction and Pricing

A split rating alone doesn’t change fundamentals; the company’s actual business remains unchanged. But markets often interpret a split as a signal of disagreement or analysis difficulty. A sophisticated investor might reason: “If the agencies can’t agree, I need more margin of safety,” leading to higher yield spreads.

In practice, pricing usually moves toward the more conservative rating. A bond rated BBB+ by S&P but A- by Moody’s will likely trade at a yield that reflects the BBB+ (lower, riskier) assessment. Buyers trust the lower rating as a warning, even if they think Moody’s has a stronger case. This is a prudent approach for risk management.

However, if the split is just one notch and both agencies rate the issuer as solidly investment-grade or solidly junk, market impact is usually muted. Traders won’t pay a large premium or discount for a one-notch debate between Moody’s and S&P within the same broad category.

Wide splits—say, A versus BB—do create pricing dislocation. The market must decide which agency is right, and this uncertainty depresses the bond’s value or widens its spread significantly.

Index Inclusion and the “Split Rule”

Bond indices determine which securities are eligible for inclusion based on ratings criteria. Most indices use a split-rating rule to handle disagreement.

The common approach is to take the lowest rating if there’s a split. So if Moody’s rates a bond A and S&P rates it BBB, the index uses BBB as the rating for inclusion purposes. This is conservative and prevents ambiguous securities from moving in and out of indices based on disagreement.

Some indices use a middle rating if three ratings exist. Moody’s A, S&P BBB, Fitch A would become BBB under a mid-rating rule. Others use a second-lowest rule, designed to tolerate single-agency outliers while still applying some discipline.

These rules have significant practical effects. If an issuer’s bond is excluded from a major bond ETF because of a split-rating rule, the ETF can’t hold it, removing a large buyer from the market and depressing price. Index managers and rating agencies are aware of this, but the rules are set to prioritize clarity and objectivity over accommodation.

When Splits Widen or Narrow

A split often widens when one agency learns new information before others. A downgrade by one agency to below investment-grade, unmatched by competitors, creates a two-or-three-notch gap temporarily. As the other agencies analyze the same developments, they typically converge toward the more conservative view, narrowing the split.

Conversely, if an issuer’s operating performance improves steadily, multiple agencies may raise ratings in sequence, converging again. A split that widens over months often signals genuine debate or one agency leading the market. A split that persists for years might indicate methodological differences that won’t resolve absent a major issuer change.

Arbitrage traders sometimes exploit splits. If they believe Moody’s will eventually downgrade to match S&P, they might short a bond maturing before the downgrade occurs, betting on a price decline. Or if they think an agency is wrong, they might take a contrarian position. These bets are risky because agency behavior is hard to predict.

Which Agency Usually Wins?

There’s no single answer, but empirically, S&P and Fitch tend to be slightly more conservative in their average ratings compared to Moody’s. This means that when a split occurs, Moody’s is sometimes the outlier on the upside. However, this is a tendency, not a rule, and it varies by sector and geography.

Historically, Moody’s was also slower to downgrade during the 2008 financial crisis, contributing to regulatory scrutiny and a reputation for being permissive. Fitch, by contrast, won early praise for more aggressive downgrading. These reputational differences persist and can influence how markets interpret a split.

For individual investors, the prudent approach is to treat the lowest rating as the basis for decision-making, recognizing that it represents the most skeptical professional assessment available.

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