New on FinoLib · Volume II: Capital Markets
My latest article is now live on FinoLib, the free finance library I write: Inverted Yield Curve and Credit Spreads Explained, from Volume II: Capital Markets. Read the summary below for the substance of the topic, then continue to FinoLib for the complete treatment.
3.5 Why an Inverted Yield Curve Predicts Recession — The Math
The idea in plain words
Normally, borrowing for longer costs more. An inverted yield curve flips that, with short-term rates above long-term ones. That means markets expect rate cuts ahead, and rate cuts usually arrive when the economy is slowing. Inversions have come before every US recession since the 1980s, by roughly 8 to 17 months. But the 2022–24 inversion, the longest and among the deepest on record, was not followed by a recession as of October 2026.
Key points
■The 10-year minus 3-month spread was inverted from October 2022 to December 2024 without an NBER-dated recession.
■The New York Fed’s model put the 12-month recession probability near 71% for May 2024; GDP grew about 3% in 2023 and 2024.
■Research disagrees on which spread matters and whether low term premia weaken the signal.
A closer look
Volume I, Part 2 noted that an inverted yield curve (short-term yields higher than long-term yields) has preceded nearly every modern US recession, and that the 2022–24 inversion was not followed by one on the usual timetable. The mathematics behind that signal: an inversion means the market’s forward rates — the implied path of future short-term rates, plus a term premium — are falling, not rising. Since short-term rates are set primarily by the central bank (Volume I’s Part 2), a market pricing in falling short-term rates in the future is collectively betting that the central bank will need to cut rates — which central banks typically only do in response to a weakening economy.
Decision rule
Reading rule: treat an inversion as a higher probability of recession over the next 6 to 24 months, not as a date. Act only when a second, independent signal confirms it, such as rising unemployment or widening credit spreads, and watch the re-steepening, which came before every recession in the 1982–2020 record. Discount the signal when the near-term forward spread is still positive or a low term premium, not expected rate cuts, drives the inversion.
The costliest mistake
Selling risk assets the day the curve inverts. Selling the S&P 500 when the 10-year minus 2-year spread inverted on July 6, 2022 (close 3,845.08) meant missing its rise to 5,616.84 by August 26, 2024, the last day of the inversion: 5,616.84 ÷ 3,845.08 − 1 = 46.1%, before dividends (FRED SP500). Avoid it: adjust risk by degrees through position size and hedges, not an all-or-nothing exit.
3.6 Credit Spreads Decomposed
The idea in plain words
A credit spread is the extra yield a company bond pays over a government bond. It pays you for three things: the risk the company won’t repay, the difficulty of selling the bond quickly, and the risk premium investors demand. Two tools measure it: the Z-spread for plain bonds, and the option-adjusted spread, or OAS, for bonds with built-in options. Past default losses explain only a small part of the spreads on investment-grade bonds.
Key points
■G-spread, Z-spread and OAS agree for a plain bond; a callable’s Z-spread includes the value of the call (46 bp in this section’s example).
■Spread ≈ default probability × (1 − recovery): a 1.06-point BBB spread implies 1.77% a year at 40% recovery versus 0.14% historical.
■Expected loss is roughly 8% to 16% of the BBB spread; the rest is liquidity and risk premium.
Decision rule
Compare credit on OAS against peers with the same rating, sector and spread duration. Buy only when the spread exceeds expected loss (default rate × (1 − R) from a rating-agency table) plus a liquidity charge you can defend, and when the loss from a stress widening (spread duration × widening, for example +150 bp on BBB) fits your risk budget. Ignore yield-to-maturity rankings for callables, MBS and ABS.
The costliest mistake
Buying a callable bond for its yield. The callable above yields 46 bp more than its straight twin with the same OAS: the pickup is option premium. If rates fall 100 bp, the same tree gives the straight bond +2.70% and the callable +1.28%; on $10 million face, $275,300 versus $128,780, so $146,520 of upside is given away for about $46,000 a year of extra yield. Avoid it: compare OAS and effective duration, not yield.
Why It Matters
Credit spreads widen sharply and immediately during periods of economic stress — well before formal downgrades — making them one of the fastest-moving, most closely watched real-time indicators of market-perceived risk across the entire corporate sector, not just for any single company.
What the full article covers
In the full article I take you through these sections:
■3.5 Why an Inverted Yield Curve Predicts Recession — The Math
■3.6 Credit Spreads Decomposed
It includes worked examples, a look under the hood at the mechanics, a clear decision rule, the one mistake that costs people the most, a recap, a reveal-on-click quiz and the official sources behind every figure.
Volume II: Capital Markets
Read the full article on FinoLib
The complete article, Inverted Yield Curve and Credit Spreads Explained, with every worked example, diagram, quiz and source, is free to read in Volume II, Capital Markets on finolib.com.
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