The S&P 500 additions included two other firms, each posting after-hours moves of about 7% and 1.8%, while several existing members were replaced as part of the quarterly rebalance.

The quarterly rebalance also affected the S&P MidCap 400, with some constituents gaining about 3.3% to 4.2% after-hours on inclusion, and others rising roughly 4.2% on news of their inclusion.

In the S&P MidCap 400, UL Solutions, Pinterest, Booz Allen Hamilton Holding, SPX Technologies, Dycom Industries, BorgWarner, and Hecla Mining Co will join the index, while Comfort Systems USA, Under Armour A and C shares, Power Integrations, Perrigo Company, Iridium Communications, Marriott Vacations Worldwide, and Insperity will be removed.

The S&P SmallCap 600 will undergo substantial changes with 13 additions and 13 deletions, adding Primoris Services, Casella Waste Systems, Indivior, Hawaiian Electric Industries, and other companies alongside removals from larger indices.

In the S&P 500, CRH, Carvana, and Comfort Systems USA will be added, while LKQ, Solstice Advanced Materials, and Mohawk Industries will be removed.

Note: The article indicates AI assistance in generation and that an editor reviewed it.

S&P said the changes are designed to ensure each index remains representative of its respective market capitalization range.

S&P Dow Jones Indices emphasizes that the changes aim to better reflect each index's market capitalization range.

No external factors or opinions are included beyond the index methodology and the list of additions and removals.

S&P Dow Jones Indices announced changes to the S&P 500, S&P MidCap 400, and S&P SmallCap 600 effective before the open on Monday, December 22, 2025, as part of the quarterly rebalance.

Carvana stock rose roughly 9% after the announcement that it will join the S&P 500, effective before market opens on December 22, 2025.