Yield curve
The yield curve is a graphical representation of interest rates, or yields, on debt securities—typically government bonds—of similar credit quality but varying maturities, with yields plotted against time to maturity.[1] It embodies the term structure of interest rates, reflecting how borrowing costs differ across short, intermediate, and long horizons.[2] In typical conditions, the yield curve slopes upward, as longer-term bonds command higher yields to compensate investors for elevated risks including interest rate fluctuations, inflation uncertainty, and reduced liquidity compared to short-term securities.[3] This normal configuration arises from expectations of stable or growing economic output, where forward rates incorporate premiums for time and potential adverse events.[4] Deviations, such as a flat or humped shape, may signal transitional economic phases, while an inversion—short-term yields exceeding long-term ones—empirically correlates with subdued future growth and recessions, having preceded every U.S. downturn since the 1950s through mechanisms like constrained bank lending and anticipated monetary easing.[5][6] Central banks and investors monitor its slope closely, as it influences lending, investment decisions, and policy calibration by distilling market consensus on inflation persistence and output trajectories.[7]Fundamentals
Definition and Core Components
The yield curve, synonymous with the term structure of interest rates, graphically represents the relationship between the yields on debt securities and their time to maturity. Yields denote the effective annualized returns to investors holding bonds to maturity, calculated as the discount rate equating the present value of future cash flows to the bond's current price. Maturities span from ultra-short durations, such as overnight interbank lending rates, to long-term obligations exceeding 30 years, with data points interpolated for a continuous curve.[8][9][10] Core components include benchmark securities, predominantly government bonds like U.S. Treasuries, which function as proxies for risk-free rates owing to the negligible default probability backed by sovereign taxing authority. The U.S. Department of the Treasury publishes daily par yield curves derived from closing market bid prices of recently auctioned securities across maturities from 1 month to 30 years. Corporate yield curves, by contrast, embed additional premia for default risk, liquidity differences, and issuer-specific factors, resulting in yields elevated above Treasury benchmarks by credit spreads typically widening with maturity.[11][12] Fundamentally, yield curves emerge from equilibrium prices in bond markets driven by supply and demand dynamics across maturities, where issuers' borrowing needs intersect with investors' willingness to lend at varying horizons influenced by risk appetites and portfolio constraints. While central banks exert direct influence on short-end yields through policy rates and open market operations, longer-term segments reflect decentralized market pricing, less susceptible to monetary policy fiat and more responsive to aggregate supply shocks and investor segmentation. Empirical analyses confirm that net bond supply variations, such as fiscal deficits increasing long-term issuance, steepen curves by elevating long-end yields relative to short-end rates.[13][14]Interest Rates, Maturities, and Basic Dynamics
The yields on short-term securities, such as U.S. Treasury bills with maturities of one year or less, are predominantly influenced by central bank policy rates, including the Federal Reserve's target federal funds rate, which directly impacts overnight interbank lending and transmits to nearby Treasury yields through arbitrage and liquidity dynamics.[15][16] For instance, adjustments to the federal funds rate, which averaged 5.33% as of September 2025, typically elicit immediate responses in short-term Treasury rates, with correlations exceeding 0.95 historically between the effective federal funds rate and the 3-month Treasury bill yield.[17] In contrast, long-term yields, such as those on 10-year or 30-year Treasury notes, reflect market assessments of sustained economic conditions, including expected inflation trajectories and real growth prospects, which drive investor demands for compensation over extended horizons.[18][19] A key observable feature of the yield curve's typical upward slope is the maturity premium embedded in longer-term rates, which arises as compensation for duration risk—the heightened sensitivity of bond prices to changes in interest rates as maturities extend. Duration, a measure of this price sensitivity, increases nonlinearly with time to maturity; for example, a 30-year Treasury bond may have a modified duration of approximately 18-20 years, compared to under 0.25 years for a 3-month bill, amplifying price volatility for equivalent yield shifts.[20] Historical analyses confirm this risk pricing: term premium estimates for the 10-year Treasury, derived from affine models using Treasury yield data since 1961, have averaged around 0.5-1.5% positive over short-term rates, correlating with observed volatility patterns where longer-maturity bond returns exhibit standard deviations 5-10 times higher than short-term counterparts during rate fluctuations, such as the 2022 yield surge.[21][22] Basic market dynamics further illustrate the interplay of rates and maturities through compounding relationships and roll-down effects in upward-sloping environments. The long-term yield i_{lt} for an n-year bond equates to the geometric mean of successive one-year spot rates via the no-arbitrage compounding formula:This holds as the internalized return from chaining short-term investments must match the direct long-term investment, absent frictions.[23] In practice, for a normal curve, roll-down returns accrue when holding intermediate-maturity bonds: as time elapses, the bond's remaining maturity shortens, shifting it toward lower-yield segments of the curve, thereby boosting its price (e.g., a 5-year bond yielding 4% rolling to 4-year status at 3.8% yield generates approximately 0.2% capital gain annually, assuming stable curve shape).[24] This mechanic, observable in periods like 2010-2019 when the 2-10 year spread averaged 1.5%, enhances total returns beyond coupon income for horizon-matched investors.[25]