[Morgan Stanley: S&P Equal-Weight Index Drops 5%, AI Concentration Risk Accumulating Before Year-End] Deep Tide TechFlow reports, according to Tide Research, Morgan Stanley's October 9, 2026, research report indicates that the S&P 500 Index fell 0.5% in September on a market-cap-weighted basis and dropped 5% on an equal-weighted basis. The top six contributing stocks collectively added approximately 190 basis points, while the remaining components collectively dragged down about 240 basis points. The median forward P/E ratio for AI and semiconductor stocks is around 32x, significantly higher than the 10-year average of approximately 19x. Morgan Stanley assesses that the AI rally remains supported by earnings, but concentration risk is accumulating. It recommends selectively holding AI positions, gradually reducing thematic concentration, tactically increasing exposure to low-volatility stocks, and allocating to financially stable value stocks to prepare for a potential turning point between December and early 2027.