Yahoo Finance·2025-10-09 14:35Core Insights - In September, the S&P 500 index rose by 3.5%, driven by strong performances from several companies [1] Company Performances - Warner Bros. Discovery saw a significant increase of 68.1% [1] - AppLovin experienced a rise of 49.2% [1] - Western Digital's shares increased by 46.6% [1] - Robinhood Markets rose by 42% due to its addition to the S&P 500 index, which necessitated purchases by index fund managers [4] - Micron Technology also increased by 42%, driven by a strong earnings report and positive management forecasts, particularly due to AI growth [5] - Intel's shares rose by 38.6%, partly due to a $5 billion investment from Nvidia and positive sentiment from Micron Technology [6] - Oracle's shares surged by 24.8% following a 359% increase in long-term performance obligations for its cloud unit, bolstered by a $300 billion agreement with OpenAI [7] - Palantir Technologies increased by 16.1%, benefiting from heightened expectations for AI growth and a strong second-quarter earnings report with a 48% year-over-year revenue increase [9]