Hartnett’s warning has real substance—this bull market propped up by 20 new high stocks has its foundation shaking.

Hartnett noted that the structure of the US stock market is similar to the peak height of the 2000 bubble. Investors should be alert to risks in the late stage of the bull market and gradually shift toward defensive allocations. At the end of May, the S&P still reached a new high, but only about 20 constituent stocks hit new highs, concentrated in AI and semiconductors. The NASDAQ’s gains of about 25% over the 4–5 months were driven by the AI chain. Breadth indicators weakened: about 55% of constituent stocks were above the 200-day line, and the advance-decline line fell back. If the high-interest-rate environment persists, or if it becomes a turning point, it is recommended to increase holdings of long-term bonds, defensive industries, and late-cycle lagging sectors to better manage a pullback.