Following the announcement of three companies joining the S&P 500 Index, the index committee has now included another new firm.

According to S&P Dow Jones Indices, Ares Management LP will be added to the benchmark index before the market opens on December 11. This move coincides with Mars Inc.'s pending $36 billion acquisition of Kellanova, the maker of Pringles and Pop-Tarts.

The announcement means Ares Management LP will become an S&P 500 constituent ahead of the three companies confirmed after Friday's close. As part of the regular quarterly rebalancing, Carvana (CVNA), CRH (CRH), and Comfort Systems USA (FIX) will officially join the index before the market opens on December 22.

Stephens analyst Melissa Roberts recently screened competing firms and identified Ares as one of the large-cap companies eligible for inclusion in the S&P 500. The index does not solely comprise major U.S. corporations—the committee has discretion in selecting new constituents as long as a company meets criteria related to profitability, market capitalization, and other factors.

Roberts' analysis suggests that the financial services sector is the most underrepresented in the index relative to its weight in the broader market.

Ares' shares surged 7% in after-hours trading on Monday. Inclusion in the S&P 500 serves as market validation for constituents and also means index-tracking funds will be required to purchase its stock.