According to Michael Hartnett, chief investment strategist of Bank of America, the current US stock market is highly similar to the top stage of the Internet foam in 2000. The S&P 500 index hit a historic high in May, but only 20 constituent stocks simultaneously hit new highs, concentrated in the AI and semiconductor sectors. In May, Micron Technology rose 87.8%, SK Hynix rose 81%, AMD Semiconductor rose 45.6%, and Samsung Electronics rose 43%. The Nasdaq rose 25% from April to May, achieving its best performance in over 20 years, but the market breadth indicator weakened. Hartnett suggests increasing long-term bonds and defensive allocation to address potential pullback risks.