When Sixteen Percent Comes in Sixty Days

1. S&P 500 up 16% over April and May (Deutsche Bank finding per CNBC) 2. This has only happened four other times since WWII 3. Last time outside a recession was before the 1987 crash 4. Shiller P/E currently at 42.53 - second highest ever, just below the 44.19 peak in December 1999 (right before dot-com crash) 5. Today's action: continued rotation, Dow up big while Nasdaq down

Now let me write this as a veteran trader who recognizes the setup.

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The S&P 500 climbed 16% between the start of April and the end of May. That magnitude of two-month gain has occurred exactly four times since the end of World War II, and the last instance outside a recession came in the months preceding October 1987. Deutsche Bank dug up the comp, CNBC passed it along this morning, and the market spent the day acting like it had never heard the news.

The stat surfaced as the Dow added another 1% today while the Nasdaq slipped 0.24%—the rotation into defensives that started yesterday accelerating into a second session. Broadcom's revenue miss and muted AI guidance sent the stock down 13% in premarket and reminded everyone that even this rally has an expiration date. The index action tells you where the fear is pooling: out of the stocks that drove the move, into the stocks that don't break when the move ends.

The setup isn't subtle. The 16% gain over April and May matches a pattern seen only four other times since 1945, with the last occurrence outside a recession appearing in the final months before the 1987 crash. Shiller P/E sits at 42.53—the second-highest print in the ratio's history, trailing only the 44.19 reached in December 1999, three months before the Nasdaq peaked and began a decline that eventually erased 78% of its value. Both comps point the same direction, and neither is reassuring.

The 1987 parallel matters because it isolates the one prior episode when a market ran this hot without a recession doing the setup work. In every other post-war instance of a 16% two-month surge, the economy was in or emerging from contraction—conditions that justify the snapback in valuations. This time, the move happened on top of an already-elevated market, in an environment where inflation remains above target and the Fed has no intention of cutting rates. Markets are pricing a 65% probability that new Fed Chair Kevin Warsh holds steady at the June meeting, with traders now positioning for potential rate hikes by mid-2027 rather than cuts.

History doesn't repeat, but valuation extremes have a way of finding their own exit. The S&P 500 has risen 10.2% since the Iran conflict began in February, climbing a wall of worry that included disrupted shipping through the Strait of Hormuz—a chokepoint for roughly one-fifth of global oil and LNG—and oil prices that recently touched $96.70 for Brent. The resilience looked like strength until you recognize it as the market pricing perfection: no recession, contained inflation despite energy shocks, rates on hold indefinitely, and earnings growth that justifies a 42.53 Shiller P/E.

That's a lot of things that have to go right. The valuation says the market believes all of them will. The 1987 and 1999 comps say that's exactly when you should start asking what happens when one of them doesn't.

• Shiller P/E mean reversion: the ratio's historical average sits at 17.38, less than half the current 42.53 reading—a gap that implies either a sustained earnings surge or a repricing that closes the distance the hard way.
• Rotation as leading indicator: the Dow climbing 1.83% while the Nasdaq falls signals capital moving toward lower-beta defensives, the trade you make when you want equity exposure but don't trust the rally to hold.
• Fed positioning into June 16-17: Warsh's first meeting as chair lands in two weeks with no cuts priced and a majority of April FOMC participants suggesting policy firming may become appropriate if inflation stays persistently above 2%.
• Energy tail risk: Iran launched fresh attacks on US bases in Bahrain and Kuwait this week following a US strike on an oil tanker, keeping the conflict live and oil supply vulnerable to further disruption.

The Deutsche Bank finding isn't a forecast—it's a frequency table. Four prior instances, one catastrophic outcome for the non-recession case, and a valuation backdrop that matches the peak before the worst bear market in a generation. You can ignore it, but you can't say the setup wasn't visible from every angle the data allows.