The US equity market reached an unprecedented $75 trillion in market capitalization - more than five times China's $14.84 trillion - with the Goldman Sachs TMT AI basket up 42% year-to-date against just 3.5% for the S&P 500 excluding AI stocks. Hedge fund portfolios show record concentration, with top-10 holdings representing 72% of exposure - a rapid-unwind risk under the melt-up.