U.S. stocks are slipping Wednesday after the Federal Reserve opted not to cut interest rates for the first time since it began trying to help the economy through easier rates in September. The S&P 500 was down 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.

The S&P 500 (SNPINDEX: ^GSPC) is widely considered the best gauge for the overall U.S. stock market. The index surged 23% in 2024 as investors reacted to the strong economy and excitement about artificial intelligence,