What the Yield Curve Shows
The yield curve plots the relationship between interest rates (yields) and maturity dates for bonds of similar credit quality — typically government bonds. The horizontal axis shows time to maturity (from one month to thirty years); the vertical axis shows the yield. Together, the points form a curve that reflects the market's current assessment of how interest rates will evolve over time.
In normal economic conditions, the yield curve slopes upward: longer-dated bonds yield more than shorter-dated ones. This makes intuitive sense — a lender who ties up money for thirty years faces more uncertainty and inflation risk than one who lends for three months, and must be compensated for it. This upward-sloping shape is called the normal yield curve.
The Inverted Yield Curve
An inverted yield curve — where short-term rates are higher than long-term rates — is one of the most closely watched economic signals in finance. It occurs when investors expect future interest rates to fall, which typically happens because they anticipate slower economic growth or recession. If the market expects the central bank to cut rates in the future, long-term bond yields fall below current short-term rates.
The inverted yield curve has a remarkable track record as a recession predictor. Campbell Harvey, an economist at Duke University, identified the predictive power of the 10-year minus 3-month yield spread in his 1986 PhD dissertation. He found that an inverted yield curve — specifically, when the 3-month yield exceeds the 10-year yield — had preceded every US recession for decades. The Federal Reserve Bank of New York maintains a public model of recession probability based on this spread.
The curve inverted in 2006 before the 2008 financial crisis, in 2019 before the 2020 Covid recession, and again in 2022–2023 ahead of a widely anticipated slowdown. Its track record, while not perfect, is better than most economic forecasting tools.
The Flat Yield Curve
A flat yield curve, where short and long rates are approximately equal, often occurs in transition periods — between a normal curve and an inverted one, or at the end of a rate-hiking cycle when the central bank has pushed short rates close to long rates. A flat curve signals uncertainty: the market is unsure whether the next move in rates will be up or down. It also reduces the incentive for banks to lend long and borrow short, which can constrain credit creation.
Term Premium and the Shape of the Curve
The yield curve's slope reflects more than just rate expectations. The term premium is the extra yield investors demand for holding longer-dated bonds — compensation for the additional duration risk (sensitivity to interest rate changes) and inflation uncertainty over a longer period.
When term premia are high, the curve steepens beyond what rate expectations alone would suggest. When term premia are compressed — as they were during the years of quantitative easing by central banks — the curve can be flatter even if rate expectations haven't changed.
The term premium is not directly observable; it must be estimated. The New York Fed publishes the Adrian, Crump, and Moench (ACM) model of the term premium, which is widely used by economists and fixed income analysts.