According to Business Insider, billionaire investor Jim Mellon recently stated that the U.S. stock market appears "severely overvalued" in his view. Despite accounting for only about 3% of the global population, the U.S. represents over 60% of the world's market capitalization. He pointed out that tech giants are experiencing extreme valuation stretches, leverage is at historically high levels, and there is a shift from their respective "moat advantages" to overlapping investments in AI data centers—all of which serve as warning signs. With Berkshire Hathaway, led by Warren Buffett, holding more than $350 billion in liquid assets, Mellon believes this in itself is a negative signal.