Rocket Companies and Affirm likely to join S&P 500 in September

Rocket Companies and Affirm Holdings each have a “medium” probability of being added to the S&P 500 during the third‑quarter rebalancing announced for Sept. 4, with changes taking effect on Sept. 18, according to Keefe, Bruyette & Woods (KBW) analysts【2】. Inclusion would force index‑tracking funds to buy the stocks, potentially lifting their liquidity and price.

KBW’s inclusion outlook

KBW notes that the upcoming discretionary changes tied to the S&P 500’s third‑quarter rebalancing could create a vacancy, prompting the index committee to consider new entrants【2】. Rocket Companies is currently the sixth‑largest firm eligible for S&P 500 inclusion and the largest eligible financial‑sector stock, underscoring its size advantage among candidates【2】. Affirm, a buy‑now‑pay‑later fintech, also meets the eligibility thresholds and is assigned a similar medium probability for the September rebalance【2】. KBW assigns a “medium‑to‑high” likelihood for Rocket’s addition over the next several quarters, suggesting a longer‑term view beyond the immediate rebalance【2】.

Market context and precedent

The S&P 500’s composition rules require a minimum market capitalization of roughly $13.1 billion, U.S. domicile, at least 50 % public float, and positive earnings in the most recent quarter and the prior four quarters【1】. When a company joins, passive funds that track the index must purchase its shares, often generating immediate buying pressure and higher liquidity【2】. Recent examples include Marvell Technology and Flex, which were added on June 22, replacing Pool Corp and Campbell’s Soup, and saw a surge in demand from index funds【2】. The broader S&P 500 now represents about $16 trillion in indexed assets, meaning any addition can shift sizable capital flows【3】.

Why the timing matters

The September 4 announcement will precede the effective date of Sept. 18, giving market participants a window to adjust holdings. With merger‑related changes expected across the broader S&P 1500, a vacancy in the S&P 500 is plausible, increasing the odds that either Rocket or Affirm will be selected【2】. Their inclusion would also diversify the index’s sector exposure—Rocket adds a large financial‑services player, while Affirm brings a fintech element—potentially influencing sector weightings that index funds must maintain【2】.

What to watch

• Sept. 4 index committee announcement – confirms whether a vacancy exists and which company, if any, is added.
• Quarterly earnings releases – Rocket’s next earnings report and Affirm’s upcoming results could affect eligibility if earnings turn negative.
• Sector rebalancing thresholds – any change in the S&P 500’s market‑cap floor (currently ~$13.1 billion) could alter the pool of eligible candidates.

The potential addition of Rocket Companies and Affirm highlights how the S&P 500’s quarterly rebalancing can reshape market dynamics, with index‑fund flows poised to amplify liquidity for the new entrants. Whether either firm secures a spot will depend on the committee’s final assessment and any emerging vacancy in the index.