S&P Dow Jones Indices will add Gulfport Energy Corp. (NYSE: GPOR) and Mobility Global to the S&P SmallCap 600, with the Gulfport entry taking effect prior to the open on Wednesday, July 1, 2026. Gulfport replaces Select Medical Holdings Corp. (NYSE: SEM), which exits the small-cap benchmark in the same rebalancing action. The changes create a mandatory buying obligation for passive funds and ETFs benchmarked to the index.
The Direct Swap: Gulfport In, Select Medical Out
S&P Dow Jones Indices named Gulfport Energy Corp. as the incoming constituent and Select Medical Holdings Corp. as the outgoing name in a direct one-for-one swap. Both companies trade on the New York Stock Exchange — Gulfport under the ticker GPOR and Select Medical under SEM.
Index changes carry mechanical consequences for passive fund managers. Portfolios benchmarked to the S&P SmallCap 600 must hold all constituents in proportion to their index weight; when a new name enters, managers are required to buy shares before the effective date to avoid tracking error. Outgoing names face the mirror-image pressure, as those same passive mandates require managers to shed the departing constituent ahead of the rebalancing date.
Mobility Global Also Enters the Benchmark
Alongside Gulfport Energy, Mobility Global is set to join the S&P SmallCap 600 as part of the same round of index changes announced by S&P Dow Jones Indices. The source does not identify which current constituent Mobility Global will replace, nor does it specify whether Mobility Global's effective date differs from the July 1 date assigned to the Gulfport–Select Medical swap.
S&P Dow Jones Indices administers the S&P SmallCap 600, a rules-based benchmark covering smaller U.S.-listed equities. Additions and deletions are announced in advance, giving market participants a window to position before the rebalancing date — an interval during which event-driven strategies typically seek to front-run the forced flows generated by passive managers adjusting their portfolios to match the updated index composition.