Concerns over rising bond yields and a top-heavy S&P 500

Almost half of S&P 500 stocks were moving differently from the overall market, one user wrote on September 25, 2026. The user said the 10 largest stocks made up around 40% of the index and argued that those companies—many riding the AI boom—could push it higher while other stocks struggled with rising yields, expensive oil and higher borrowing costs.

A separate post that day claimed $370 billion had been wiped from the US stock market in nine minutes and said rising bond yields were putting pressure on stocks.