Wall Street's Earnings-Bubble Warning May Hit 60/40 First

Goldman Sachs' earnings-bubble warning is coming from inside bullish camp

The warning is coming from an unlikely place: Wall Street's own bull camp. Goldman Sachs chief global equity strategist Peter Oppenheimer conceded earlier this month that there may be an earnings bubble in technology even if traditional valuation metrics do not yet indicate one. That matters because markets often turn not when assets look expensive, but when the story investors paid for starts to crack.

On the surface, the market still looks constructive. The S&P 500 has advanced almost 11% this year, EAFE returned 7%, and emerging market stocks climbed 23%. Global equity returns are solidly good, which helps explain why investors have been willing to stay risk-on.

That comfort may be the trap. Bulls can point to resilience and broader participation. But investors have also been anchored to a two-decade script in which tech leadership led through stress and bonds protected the portfolio. Now the 60-day correlation between the S&P 500 and Treasury returns is near a more-than-two-decade high, so the old safety net is less dependable.

The first rejection in a market like this is usually behavioral. Investors are not just checking valuation; they are testing whether their favorite narrative still holds together.

Why the 40 in 60/40 may stop working first

The practical problem is no longer abstract. Even after the Fed kept rates at 3.50% to 3.75% earlier this week, expectations have shifted from cuts to the possibility of further hikes. BofA Global Research now expects three rate increases of .25% each in 2026, starting in September. At the same time, longer-term bonds are demanding more compensation for inflation and term risk. Reuters reports that long-dated bonds have come under pressure as investors demand more compensation for inflation, U.S. economic strength and expected increases in bond supply driven by deficit spending.

That is a hard backdrop for the "40" in a 60/40 portfolio. Bonds are supposed to help stabilize a portfolio when equities stumble, not ask investors to absorb fresh rate risk at the exact moment stocks wobble.

Why the hedge is fraying

The bond-market signal is straightforward: investors want more pay for holding longer-duration debt. Reuters also reports that the 30-year U.S. Treasury yield rose further above 5% before drawing buyers back in. If that environment persists, the traditional role of bonds becomes harder to rely on.

This is not just a portfolio-weights debate. The familiar stock-bond diversification assumption is under strain, with the negative correlation between stocks and Treasuries diminished and the 60-day correlation near a more-than-two-decade high. If both asset classes can fall together, the portfolio math changes quickly.

The behavioral trap behind the old 60/40 faith

From 1982 to 2021, declining interest rates turned bonds into a tailwind, giving the classic 60/40 portfolio a surprisingly reliable support system. That history made bonds easy to treat as a default shock absorber.

Bulls still argue that bonds remain useful for rebalancing and volatility control, especially because stocks are risky and bonds are less risky, so the mix helps match portfolio risk to tolerance. But that logic can become a trap if investors assume the hedge will work the same way in a higher-rate, less-collaborative stock-bond regime.

What to watch if the 60/40 narrative starts to break

The right approach is not to call a selloff in advance. It is to watch whether the market's favorite story is losing support faster than position changes show up in headlines.

Five signposts to monitor

1) The long end stays hot. If the 30-year U.S. Treasury yield rose further above 5% environment returns and holds, bonds are still signaling that investors need more compensation for duration and inflation risk.

2) Stocks and bonds stop moving apart. If the 60-day correlation between the S&P 500 and Treasury returns remains near its more-than-two-decade high, diversification is still more psychological than statistical.

3) Breadth stops confirming the tape. Yes, global equity returns are solidly good, and IPO activity has been strong enough to suggest enthusiasm is broadening beyond a few mega-cap names. But if leadership narrows again, investors may have to admit that recent breadth created a false sense of security.

4) The Fed narrative shifts from steady to tighter. The Fed kept rates at 3.50% to 3.75% earlier this week, yet rate expectations have broadly shifted from cuts to potential increases later this year. If that drift strengthens, the market has to reprice under a more hostile funding backdrop.

5) AI capex faces harder earnings proof. Goldman's bull-strategy camp now says there may be an earnings bubble in tech even without an obvious valuation bubble. The key test is whether spending power keeps translating into durable earnings quality.

What a more defensive posture would look like

Stay alert, not panicked. If the bond market keeps demanding higher compensation, the practical response may be more selectivity rather than blind faith in reflexive diversification. In bonds, some investors favor shorter maturities if Treasuries are still meant to anchor the portfolio. In equities, favor companies that can substantiate earnings durability above the AI capex narrative, and keep some cash or hedges available.

The clean invalidation signal is also clear: if long yields cool, stock-bond correlation falls, and breadth plus tech earnings continue to validate the current story, then the warning may be less urgent than it appears.