Nvidia and other U.S. tech stocks are holding steadier Tuesday, a day after tumbling on doubts about whether the artificial-intelligence frenzy really needs all the dollars being poured into it. The S&P 500 was 0.

Warren Buffett's historic $127 billion warning to Wall Street happens to align with another stock market alarm. Specifically, the S&P 500 currently trades at a historically expensive valuation. The index achieved a cyclically adjusted price-to-earnings ratio (CAPE) of 37.9 in December 2024, which is a substantial premium to 20-year average of 27.

Here’s a surprising new fact about the world’s largest and most-liquid public equity market: Most of the activity on it isn’t public anymore.