Why the 60/40 Debate Is Focused on the Wrong Statistic

Rising interest rates have revived calls to abandon the traditional 60/40 portfolio of US stocks and bonds. The argument sounds straightforward: if stock-bond correlations remain higher than before 2022, then bonds no longer reliably cushion equity losses. But that conclusion relies on a narrow reading of one statistic. Correlation measures whether two assets tend to move in the same direction, not how large those moves are or whether the shared direction is helpful or harmful.

The recent data make this clear. Stocks and bonds lost money together in about 14% of months over the past 25 years, but that figure jumped to 28% over the past five years during the 2022 inflation-driven selloff. Over the past three years, simultaneous losses have become less frequent at 22% of months. At the same time, both asset classes rose together in 50% of months over the past three years, up from 43% over five years and 40% over 25 years. Higher correlation, in other words, also reflects more months when stocks and bonds are both gaining.

What matters for portfolio risk is not co-movement alone but how bonds behave during the market's worst stretches. Over the past three years, when stocks fell nearly 5% on average in their worst 10% of months, core bonds declined about 1.7%—roughly one-third as much. That is a smaller cushion than investors received during earlier periods, but it is still a meaningful reduction in portfolio damage. Consider a $100,000 60/40 portfolio. In such a month, the $60,000 stock allocation would fall to about $57,000, while the $40,000 bond allocation would fall to roughly $39,300. Because bonds held up better, they would become about 41% of the portfolio, creating a small but real opportunity to sell bonds and buy cheaper stocks.

What Bond Returns Actually Delivered in the Worst Equity Months

The Blind Spot in the Correlation Statistic

Correlation is frequently used as a shorthand for diversification, but it omits two critical pieces of information. First, it says nothing about the size of losses or gains. Second, positive correlation can appear in both good and bad markets. Stocks and bonds can move together because both are rising, which is harmless for investors, or because both are falling, which is painful. The recent rise in stock-bond correlation has been driven partly by more months when both assets rose, not only by shared losses. That distinction matters when deciding whether a diversified portfolio has actually broken down.

What 2022's Inflation Shock Did—and Didn't—Break

The 2022 selloff was unusual because aggressive Federal Reserve rate increases pushed stocks and bonds down together. Over the past five years, that period pushed simultaneous losses to 28% of months, well above the 14% long-term average. But the pattern has softened over the past three years, with simultaneous losses falling to 22% of months. The key point is not that bonds have returned to their historical role in full—they have provided less downside protection than they did before the inflationary shock—but that they have continued to lose less than stocks when markets become stressed. If inflation remains sticky, that cushion may stay thinner than in the past, but the underlying mechanism still functions.

Why 'Losing Less' Is a Real Diversification Cushion

Bonds do not need to gain during every equity decline to add value to a portfolio. They need to fall less than stocks, which limits the overall drawdown and preserves capital that can be redeployed into cheaper equities. In the $100,000 60/40 example, a severe stock month would leave bonds at roughly 41% of the portfolio rather than the 40% target. Rebalancing would involve selling about $900 of bonds and buying stocks to restore the 60/40 split. The rebalancing opportunity is smaller than it was when bonds often rose during equity selloffs, but the risk-management logic remains intact: the cushion exists, and the rebalancing mechanism still creates a systematic way to buy equities after they have become cheaper.

What Long-Term Investors Can Do With the 60/40 Math

For individual investors, the data argue against abandoning bonds simply because the correlation number looks different from the pre-2022 era. The practical steps follow directly from the portfolio math.

  • Judge your bond allocation by its behavior during equity drawdowns, not by monthly correlation. Over the past three years, core bonds fell about one-third as much as stocks in the worst equity months, so a positive correlation figure alone should not trigger a sale.
  • Keep a rebalancing rule tied to actual portfolio drift. In the $100,000 60/40 example, a severe stock month left bonds at about 41% of the portfolio; selling around $900 of bonds and buying stocks would restore the target and purchase equities after they fell.
  • Set realistic expectations if inflation remains elevated. The recent three-year data show a smaller cushion than the pre-2022 norm, so bonds may not provide the same magnitude of protection unless the inflation regime changes.
  • Do not replace core bonds with riskier assets simply because correlation has risen. The source data show bonds still lost far less than stocks in the market's worst stretch, which is the specific protection a balanced portfolio is designed to provide.