The S&P 500 reached a new closing high at the end of May, driven by a limited number of stocks, echoing conditions reminiscent of the 2000 dot-com bubble peak. According to Bank of America strategist Michael Hartnett, only 20 stocks reached new highs alongside the index, with AI-related sectors, particularly semiconductor and memory chip companies like AMD and Micron, leading the charge. Despite the Nasdaq Composite Index's impressive 25% rise over April and May, market breadth remains weak, with only 55% of S&P 500 components trading above their 200-day moving average as of May 20. Analysts suggest this narrow rally could signal underlying market fragility, prompting recommendations for investors to consider shifting towards defensive assets as the market approaches potential peaks.