Update: September 8, 2025.
The announcement by S&P Dow Jones Indices, reported by S&P Dow Jones Indices and confirmed by Reuters, includes the addition of Robinhood Markets (HOOD) to the S&P 500.
The operation, expected to generate a double-digit rally and volumes above the recent average, is scheduled for the quarterly rebalancing in September 2025, with execution at the opening on Monday, September 22, 2025.
In this context, the time frame remains a central element for price discovery and for the adjustment of indexed portfolios.
According to data collected by our quantitative research team, the quarterly S&P rebalances in recent years have shown increases in intraday volumes for the included stocks, with short-term effects often measurable in days.
Industry analysts note that, in addition to mechanical flows, existing liquidity and the share of AUM that physically replicates the index matter: SPY, the largest S&P 500 ETF, had over 300 billion dollars of AUM at the end of 2024, which makes the flows potentially significant for mid-cap stocks.
These operational observations derive from the analysis of past executions and the pro-forma files published by S&P DJI.
What was decided (and with which substitutions)
S&P Dow Jones Indices has announced that, in the September quarterly rebalancing, Robinhood is expected to enter the S&P 500 along with AppLovin (APP) and EMCOR Group (EME).
The three stocks will replace Caesars Entertainment (CZR), MarketAxess (MKTX), and Enphase Energy (ENPH), according to the data provided in the official documents announced and illustrated by Reuters. That said, the composition highlights a cross-sectional rebalancing by capitalization and sectors, in line with S&P DJI procedures.
Schedule and Operating Methods
The changes should be implemented at the opening on Monday, September 22, 2025, in conjunction with the quarterly rebalancing of the S&P 500.
As usual, S&P DJI publishes pro-forma files and technical details well in advance to facilitate execution by indexed managers; the pro-forma files are available on the official S&P DJI website. Indeed, the implementation window and pre-rebalancing communications aim to ensure transparency and operational coordination.
Effects on HOOD Stock: Short vs Medium Term
In the short term, the anticipated index inclusion tends to generate passive flows and increased liquidity.
ETFs and funds that replicate the S&P 500 might proceed with purchases to realign the weight determined in pre-rebalancing documents, increasing visibility among institutional investors and sell-side coverage, although there might be an episode of high volatility around the effective date (front-running and after-flow phenomena).
It should be noted that the adjustment dynamic may not be linear, especially in the hours close to the opening.
- Purchases by ETFs and funds that replicate the S&P 500, with realignment to the weight of HOOD.
- Increased visibility among institutional investors and sell-side coverage.
- Risk of increased volatility around the expected effective date.
In the medium term, the performance of the stock will depend on the fundamentals: growth of the user base and deposits, performance on revenues from trading and interest, development of crypto services, and unit economics (such as margins and cost-to-serve).
In this context, the quality of strategic execution remains the discriminating factor for the trajectory of HOOD.
How Passive Flows Work
The main ETFs and index funds linked to the S&P 500 manage hundreds of billions of dollars. The mechanical demand is calculated as replicating AUM multiplied by the floating weight of HOOD (determined by S&P DJI based on floating capitalization and sector).
The precise weight will be defined in the rebalancing files and may vary depending on prices until the expected effective date. In summary, the size of the flows depends on known variables, but they are formally updated only in the pre-rebalancing documents. For more information on the mechanism of passive flows, see our internal guide on passive flows and rebalancing.
History of Inclusions: What It Teaches Us
Historically, inclusions in the S&P 500 have generated a positive “announcement effect,” followed by a possible partial reabsorption in the following weeks.
The magnitude of the effect varies based on the size, liquidity of the stock, and the share of AUM that physically replicates the index. Yet, the patterns remain heterogeneous and often sensitive to the market context and the microstructure of the stock involved.
Impact on the Market and Other Involved Securities
AppLovin and EMCOR Group contribute to expanding the sector diversification of the index (software/digital advertising and engineering services), while the exits of Caesars, MarketAxess, and Enphase Energy lead to a redistribution of weight towards sectors such as consumer discretionary, financials, and renewable energy.
The incoming stocks are expected to benefit from increased analytical coverage and liquidity, while those exiting may experience technical pressure due to the unloading of indexed funds. In this context, the adjustment of the baskets replicates the evolution of the free-float capitalization and the represented segments.
Main Risks to Consider
- Technical reversal after the peak due to the announcement and the effectiveness of the operation.
- Execution risk on the rebalancing day, with possible gaps and slippage.
- Impact of regulation and retail/crypto trading dynamics on Robinhood’s revenues; for regulatory updates, see our overview on fintech regulation.
What to Monitor in the Coming Weeks
- Volumes and order book around September 22, 2025.
- Revenue, EPS, and active user trends in the quarterly results; see the earning reports page for deadlines and official announcements.
- Updates S&P on float-adjusted weight and pro-forma files pre-rebalancing (refer to the S&P DJI website for official files).
Quick Summary
- Scheduled inclusion date: September 22, 2025 (at market open).
- Enter: Robinhood (HOOD), AppLovin (APP), EMCOR Group (EME).
- Exiting: Caesars (CZR), MarketAxess (MKTX), Enphase Energy (ENPH).
- Main market drivers: passive flows, increased liquidity, and potential tactical volatility.
Editorial note: Weights, flows, and precise figures (percentage change and volumes on the day of the announcement) will be updated as soon as they are available in the official documents.