S&P 500, MidCap 400, and SmallCap 600 Welcome New Members as Indexes Rebalance for 2026

On Dec. 5, S&P Dow Jones Indices announced the companies that would be joining and leaving the S&P 500 Index (SPY), S&P MidCap 400 Index (MDY), and S&P SmallCap 600 Index (VIOO) effective Dec. 22, 2025. Now in the first full trading week of 2026, the major S&P indexes have all been rebalanced and welcomed new members, including Carvana (CVNA), Comfort Systems USA (FIX), and CRH (CRH), among others. Why Does the S&P 500 Rebalance? It's crucial for investors to understand why the S&P 500 or any index rebal ...