US stocks have almost never moved this independently of each other: The S&P 500's 6-month implied correlation is down to 0.15, an all-time low. Implied correlation measures how closely stocks are expected to move together, with a reading this low meaning individual stocks are becoming increasingly disconnected from the broader index. This metric has now more than HALVED over the last 4 months, when correlation was at 0.35 during the market selloff. By comparison, the long-term average stands at 0.43, nearly 3 times the current level, while the high over this period was 0.82 during the 2020 pandemic crash. This historic divergence highlights a market increasingly driven by a handful of mega-cap stocks, while the rest of the market trades more on its own fundamentals. Market concentration has rarely been this extreme.