Bond-Equity Correlation
Bond-Equity Correlation
For two decades, bonds and stocks moved in opposite directions: when equities fell, bonds rose. In 2022, that regime ended, and both fell together.
Key takeaways
- Bond-equity correlation from 2000 to 2021 averaged near zero or negative, making them effective portfolio hedges
- The negative correlation was driven by Fed intervention: falling growth expectations led to rate cuts and bond rallies
- 2022 broke the pattern: both bonds and stocks fell as inflation and rate hikes dominated
- Stagflation and growth shocks historically correlate bonds and stocks positively—both assets suffer
- Understanding the current regime is critical to portfolio construction and rebalancing discipline
The post-2000 negative correlation era
From roughly 2000 through 2021, the correlation between U.S. bonds and U.S. stocks was either flat or negative. This was a gift to diversified portfolios. When the economy weakened and stocks fell, the Federal Reserve typically cut rates, which pushed bond prices higher. The classic examples are 2001–2002, 2008–2009, and March 2020.
In March 2020, the S&P 500 fell 34% in six weeks as COVID lockdowns spread. Simultaneously, U.S. Treasury bonds rallied about 8%. The 10-year yield fell from 1.7% to below 0.5%. This wasn't because bonds were inherently more resilient; it was because investors fled to safety and the Fed stepped in with rate cuts and balance-sheet expansion. The correlation between daily returns was sharply negative: the worse stocks performed, the better bonds performed.
This regime persisted through the 2010s and early 2020s. In the 2018 "rate shock," stocks fell 20% (December), and bonds rose 1–2%. In the 2020 COVID crash, the relationship held. But the mechanism was always the same: Fed stimulus drove rates down, and lower rates benefited bond prices.
Quantitatively, rolling 12-month correlations between the S&P 500 and AGG (Aggregate Bond Index) from 2000 to 2021 spent most of their time between −0.3 and +0.2. For a portfolio builder, this was remarkably benign. It meant that the ballast worked as advertised.
Why the post-2000 negative correlation occurred
The mechanism was not mysterious. In the post-2000 world, central banks had become powerful tools against cyclical downturns. When growth weakened, rates fell. When rates fell, bond prices rose. This inverse relationship between growth and rates created an inverse relationship between stocks and bonds.
Consider the 2008 crisis. Fed funds fell from 5% to near 0%. The 10-year Treasury yield collapsed from 3.6% to 2%. Long-duration bonds, particularly the intermediate and long-dated bonds in AGG and BND, soared in price. An investor holding bonds in 2008 experienced a portfolio loss that was substantially smaller than an equity-only investor, even though both asset classes faced a credit crisis. The bond rally wasn't about safety in absolute terms; it was about the Fed cutting rates.
This regime also reflected a period of generally low inflation. From 2009 to 2021, inflation averaged around 2% annually in the developed world. Central banks had room to cut and maintain real returns. Inflation expectations were anchored. A stock market downturn was typically a growth shock, not an inflation shock—and growth shocks invited policy easing, which lifted bonds.
The 2022 regime break
Everything changed in 2022. Inflation surged above 8%. The Fed, having cut rates to near zero in 2020, was forced to raise them aggressively. The federal funds rate went from 0% in December 2021 to 4.3% by year-end 2022. The 10-year yield rose from 1.5% to 3.9%. This dual assault—falling growth expectations and rising rates—struck both bonds and stocks simultaneously.
The data tells the story. In 2022:
- S&P 500: down 18%
- AGG (broad bonds): down 13%
- 10-year Treasury: down 16% (price basis)
- Correlation between daily S&P 500 and AGG returns: +0.3 (positive, moving together downward)
This was the worst environment for a diversified portfolio in decades. The ballast had failed. A 60/40 portfolio fell 16%; a 100% equity portfolio fell 18%. The ballast still provided a modest cushion, but it was no longer a hedge.
Why did the correlation turn positive? Because the shock that drove markets down was inflation and monetary tightening, not a growth shock. In a growth shock (2008, 2001, 2020), stocks fall because earnings expectations collapse, and the Fed cuts rates to cushion the blow—bonds rally. In an inflation shock (2022, 1970s), stocks fall because higher rates and inflation expectations reduce valuation multiples, and bonds also fall because their coupons are now worth less in real terms and their prices fall as rates rise. Both assets suffer on the same fundamental signal.
Historical correlation regimes
Periods of sustained positive bond-equity correlation are rare in modern history but instructive:
1973–1974 (stagflation): Both stocks and bonds fell. The S&P 500 dropped 48%; intermediate bonds fell 3–5%. Inflation surged while growth stalled. The 10-year yield rose from 6% to 8%, pushing bond prices down even as investors fled equities.
2022: As discussed, both fell simultaneously.
2023–2024 (mixed regime): As inflation cooled, the Fed hinted at rate cuts, and the correlation returned toward neutral and slightly negative. This illustrates the key principle: the regime is not permanent.
Measuring correlation correctly
Correlation is often cited carelessly. A one-year correlation of +0.3 is not the same as a crisis correlation. During market panics, correlations often spike—assets that are usually diversifying suddenly move together as investors liquidate everything. Conversely, rolling correlations computed over long periods (5+ years) can obscure short-term regime shifts.
For portfolio construction, what matters is the correlation you expect going forward, not the historical average. If you believe inflation will remain elevated and the Fed will keep rates higher for longer, the regime from 2022 may persist: positive or neutral bond-equity correlation. If you believe disinflation is underway, the old negative correlation may return.
The practical implication: don't build a portfolio on the assumption that bonds will always hedge equities. They often do, but in stagflation, they don't. This is why bonds are ballast, not insurance.
Flowchart: Bond-Equity Correlation Drivers
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