Crédito: Jeenah Moon para Newsday
La distribución de las inversiones entre las clases de activos puede reducir el riesgo y suavizar los rendimientos. La clásica diversificación entre acciones y bonos funcionó históricamente porque se movían en direcciones opuestas. Cuando las acciones cayeron, los inversores buscaron seguridad en los bonos. Los bonos se recuperaron, amortiguando las pérdidas y estabilizando las carteras.
Desde el comienzo del período pandémico, con choques de oferta que alimentaron la inflación, los bonos se han vuelto menos efectivos para amortiguar la volatilidad de las acciones. En lugar de compensar el riesgo de capital, los bonos se mueven cada vez más en conjunto con las acciones. Este cambio es particularmente pronunciado durante las fuertes ventas de los mercados, con profundas implicaciones tanto para los inversores como para los responsables políticos.
El desglose de esta relación histórica hace que la diversificación -como la cartera clásica, de acciones del 60% y bonos del 40%, o estrategias de paridad de riesgos- sea vulnerable a los choques. Las estrategias de inversión en fondos de cobertura y paridad de riesgos que emplean un apalancamiento basado en la relación histórica ahora se mueven cada vez más en conjunto con los rendimientos del Tesoro, lo que podría hacerlos vulnerables al desapalancamiento forzado.Incluso los inversores institucionales conservadores, como los fondos de pensiones y las aseguradoras, podrían estar expuestos a una mayor volatilidad de la cartera durante las correcciones del mercado.
Las correcciones tienden a ser agudas, acompañadas de un aumento de la volatilidad del mercado de valores. Esto amplifica las vulnerabilidades sistémicas, ya que la volatilidad puede alimentar la dinámica de las ventas al empeorar las limitaciones de financiación de los inversores y forzar el desapalancamiento.
Mirando hacia atrás, nuestro análisis muestra que el punto de inflexión para las correlaciones se produjo a finales de 2019. Con el inicio de la pandemia al año siguiente, la relación histórica cambió significativamente, lo que dio lugar a fuertes ventas de acciones y bonos con mayor frecuencia.
From 2000 to 2019, the inverse relationship between expected stock and bond returns helped investors effectively manage risk. Tracing standardized expected returns for stocks and bonds against the VIX shows a clear divergence: As volatility rises, expected returns for equities increase as stock prices fall, while expected returns for bonds decline as bond prices rise. This was the foundation of diversification strategies.
The changed relationship since 2020—with both asset classes tending to sell off concurrently in response to rising market stress—reinforces equity risk in the United States as well as, to varying degrees, Germany, Japan, and the United Kingdom.
This breakdown may explain the severity of recent market selloffs: losses compound when both assets fall together.
The diminished hedging properties are increasingly evident in the sharp rallies in gold, silver, platinum and palladium, as well as currencies such as the Swiss franc. Gold, for example, has more than doubled since the start of 2024 as investors sought alternative safe havens in recent months. Platinum and palladium jumped in the final quarter of last year, reflecting diversification shifting toward non-sovereign stores of value.
Diminished protection
Amid the hedging breakdown, higher volatility coincides with higher expected bond returns, with prices declining steeply in the current period as investors reprice term premiums.
Over the past few years, expanding bond supply to finance widening fiscal deficits across most advanced economies, which we also explored in the October 2025 Global Financial Stability Report,has heightened investor concerns. At the same time, gross issuance of bonds has outpaced central bank balance-sheet runoff, that is, bonds maturing without reinvestment.
With central banks reducing holdings via runoff, a larger share of bond supply must be absorbed by price sensitive private investors. This gap has become more evident since late 2023 as central banks’ balance sheet runoff slowed while issuance stayed elevated. Overall, the supply absorbed is many times larger than the reduction in central bank holdings over the past few years in the four largest advanced economies.
With inflation still above target in many economies, fiscal concerns increasingly raise term premiums as investors see bonds as riskier, eroding their suitability for hedging. Investors may demand higher compensation for holding longer maturities, reinforcing upward pressure on term premiums and further eroding hedges.
With fiscal expansion expected to continue, this upward pressure may be reinforced if corporate capital investment is increasingly financed by debt issuance. These effects could be reduced by greater productivity growth, bringing down inflation and allowing government to issue bonds with shorter maturities.
Policy challenges
Central banks will undoubtedly intervene to stabilize bond markets during periods of extreme stress, but this has limits. Relying on emergency measures can lead to excessive risk-taking and undermine market discipline.
A more durable solution, restoring the hedging properties of sovereign bonds, requires fiscal discipline. High debt levels globally and uncertain fiscal trajectories weaken the safe-haven status of government securities. Without credible fiscal frameworks, bonds cannot serve as reliable anchors in turbulent markets.
Central banks also must commit to ensuring price stability. The unexpected rise of inflation since 2020 has been a key contributor to the reversal in stock-bond correlations.
Regulators should also incorporate correlation breakdown scenarios into stress tests. Financial institutions need to prepare for traditional diversification to fail, as models calibrated on historical correlations may underestimate new risks.
Rethinking risk
With diminished diversification, investors must build portfolios that account for the shift in correlations. Alternative strategies—such as incorporating commodities or private assets—may offer partial solutions, but they come with their own complexities and risks.
Policymakers face even greater challenges. Maintaining financial stability amid high correlation risk requires credible fiscal and monetary policy frameworks, robust stress testing, and clear communication to anchor expectations. If diversification fails, volatility can cascade into broader financial instability. Investors and policymakers must rethink risk management for a new era where traditional hedges fail.
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