Robinhood remains outside the Wall Street benchmark index while Interactive Brokers enters the S&P 500: the market reacts immediately, with forced purchases by large ETFs and sales on stocks linked to bitcoin.
According to the data collected by our team of market analysts, similar announcements typically show spikes in intraday volatility and a significant increase in volumes on selected stocks in the 24–48 hours following the announcement.
The industry analysts we collaborate with also report that, with equal capitalization, a stock’s ability to absorb passive flows (liquidity and float) is often decisive in the committee’s judgment.
What happened
In the latest update communicated by S&P Dow Jones Indices, Interactive Brokers (IBKR) was chosen for entry into the S&P 500, replacing Walgreens Boots Alliance. Robinhood (HOOD), indicated by some observers as a possible candidate, was not included.
It should be noted that the news produced immediate reactions in extended trading: IBKR achieved approximately a +4% in after-hours (exact quantities subject to real-time verification), while there was pressure on stocks more exposed to the crypto sector.
Why it matters: ETFs, forced buying, and volatility
The entry into the S&P 500 requires ETFs and index funds that replicate the index (including SPY, IVV, VOO) to buy the stock in line with the weight assigned in the index. The combined AUM of the main replicators exceeds 1.2 trillion dollars (data updated 2025), triggering significant flows and potential bull/bear adjustments near the effective date. In this context, passive operations can increase short-term volatility.
The criteria to enter the S&P 500 (2025)
Inclusion is not automatic: a committee applies official guidelines and a discretionary judgment on the representativeness of the stock. Among the key requirements:
- Free-float capitalization at least equal to the current minimum threshold.
- Domicile and quotation in the United States, with adequate reporting standards.
- Adequate liquidity: sustained volumes, available float, and tight spreads.
- Consistent share structure (common shares, float requirements).
- Profitability and operational continuity in compliance with S&P guidelines.
- Discretionary evaluation on sector, stability, and representativeness of the index.
Capitalization threshold: the bar rises to 22.7 billion
Starting from August 25, 2025, the minimum capitalization threshold for admission is updated to approximately 22.7 billion dollars. The stated goal is to keep the S&P 500 focused on the most liquid large cap, reducing the entry of issuers that are too small.
The Robinhood case and crypto-related stocks
On Robinhood, there were expectations of entry, fueled by the stock’s rally and its increased presence in the retail and crypto ecosystem.
The lack of selection triggered after-hours sales on the stock and on names with high correlation to Bitcoin, such as MicroStrategy (MSTR), already affected by the decline of the cryptocurrency. An interesting aspect is that the committee’s choice indicates how, with equal capitalization, elements such as liquidity, float profile, and sectoral representativeness may have favored the inclusion of IBKR.
Numbers to monitor for HOOD
- Free-float capitalization compared to the threshold of $22.7 billion (effective from August 25, 2025).
- Average daily volumes and bid-ask spread on an intraday basis.
- Available float and presence of controlling shareholders.
- GAAP Profitability on a trailing 4-quarter basis.
- Volatility and sensitivity to crypto and retail cycles.
Suggested sources: company reports (Investor Relations), stock market data pages, Yahoo Finance / Bloomberg. To further explore the impact of ETFs on the markets, also see the market notes on ETF flows.
Why some companies stay out
The lack of inclusion may result from a non-full compliance with one or more requirements or from a discretionary choice aimed at preserving the sectoral balance of the index. It should be noted that factors such as limited float, insufficient liquidity, or profitability not in line with S&P standards can weigh more than simple capitalization.
The overview in brief
The Robinhood – S&P 500 case highlights a tightening of entry criteria: with the threshold of $22.7 billion and with increasing attention to liquidity, the committee tends to favor issuers capable of absorbing significant passive flows without price distortions.
The entry of IBKR and the exit of Walgreens Boots Alliance show an index in constant update to adhere to the real market structure. In this context, for investors, the point is clear: technical criteria and timing matter as much as, if not more than, the short-term narrative.
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Source: https://en.cryptonomist.ch/2025/08/26/robinhood-out-of-the-sp-500-ibkr-soars-crypto-stocks-down/
