The Nasdaq Composite closed at 27,232.71 on September 22, its highest level on record and more than 1,200 points above where it stood the day the Federal Reserve raised interest rates for the first time in over three years. A rate increase built partly on the argument that inflation has run too high for too long is, in most cycles, the kind of signal that cools a crowded trade. This time the index kept climbing through it.
The Signal the Rally Is Not Pricing
Fed Chair Kevin Warsh was direct about the reasoning behind the September 16 decision. Inflation, he said, is too high and has been for too long, exceeding the Fed's target for five years. The committee voted unanimously to raise the policy rate to a range of 3.75 to 4 per cent and signalled at least one more increase before the year is out.
Higher rates raise the discount applied to future earnings, which should weigh hardest on the most richly valued, most speculative names in the market. Those are precisely the names that have led the advance. Instead of pausing to digest the decision, the index closed higher in four of the next five sessions.
The Nasdaq shows what is happening to the price of AI-linked growth stocks specifically, and the pattern this month traces a clean line from the Fed decision to the highs that followed it.
The Nasdaq Composite closed at 27,232.71 on September 22, 2026, up from 25,978.43 on September 16, the day the Federal Reserve raised its policy rate to the 3.75 to 4 per cent range. Source: Nasdaq, Yahoo Finance.
Why Recent Gains Crowd Out the Warning
Amos Tversky and Daniel Kahneman, publishing in 1979, described how people weight recent, vivid information far more heavily than base rates or structural signals. In a market context, that means five sessions of gains after a rate hike carry more felt weight for an investor than the hike itself, even though the hike is the more informative event about what happens next.
Richard Thaler's work on mental accounting adds a second layer. Investors who have already booked large unrealized gains in AI-linked names tend to treat those gains as house money, a separate mental account they are more willing to risk than fresh capital. That framing makes it easier to hold through a warning that would otherwise prompt trimming a position.
What the Named Warnings Actually Say
Capital Economics is not a fringe voice. Senior markets economist James Reilly screened eight categories of market indicators this month and found most sitting at or near levels last seen at prior cycle peaks. The firm's house view is that the S&P 500 cracks within the next year and eventually falls at least 30 per cent from its high.
Acadian Asset Management's Owen Lamont has taken a different angle, documenting the frequency of unusually large daily swings in individual names rather than the index level itself. He calls the current stretch crazy days, a description aimed at market structure rather than valuation, and it points to the same underlying fragility other analysts are flagging through different data.
Not every house agrees. Morgan Stanley Wealth Management has kept a year-end S&P 500 target of 8,000, with Chief Investment Officer Lisa Shalett arguing the market is pricing known risks in clear-eyed fashion rather than ignoring them. The disagreement between comparably credentialed firms is itself informative. It means the current price reflects a real debate, not a consensus that has simply gone unquestioned.