Bank of America (BofA) reported that only 44% of large-cap active funds outperformed their benchmarks in September, due to a sharp concentration of market dominance in mega-cap stocks. The market-cap-weighted S&P 500 Index outperformed the equal-weighted S&P 500 Index by nearly 5 percentage points. Growth fund managers were most affected, with Meta and AMD contributing 70% of the Russell 1000 Growth Index's monthly gains.