According to @MilkRoadDaily, Robinhood Markets (HOOD) will be added to the S&P 500 effective Sept 22, marking a notable milestone for the brokerage, source: @MilkRoadDaily on X. For trade execution planning, S&P 500 index-tracking funds typically adjust holdings to include new constituents on or around the effective date, which can drive mechanical demand and concentrated closing-auction activity, source: S&P Dow Jones Indices. For crypto-focused market participants, Robinhood also offers crypto trading in assets such as BTC and ETH, making the development relevant when monitoring equity proxies for retail trading engagement, source: Robinhood Crypto.

According to @EricBalchunas, MicroStrategy ($MSTR) was not admitted to the S&P 500 despite meeting criteria because the S&P Index Committee declined the addition (source: Eric Balchunas on X, Sep 5, 2025). The S&P Dow Jones Indices methodology confirms the S&P 500 is selected by a committee with discretion to deviate from mechanical rules, effectively making SPX an actively chosen basket within stated guidelines (source: S&P Dow Jones Indices, S&P U.S. Indices Methodology). Without inclusion, S&P 500 index-tracking funds will not purchase MSTR as part of routine rebalancing, limiting automatic passive inflows relative to an inclusion scenario (source: SPDR S&P 500 ETF Trust SPY, iShares Core S&P 500 ETF IVV, and Vanguard S&P 500 ETF VOO prospectuses). S&P Dow Jones Indices notes that trillions of dollars are indexed or benchmarked to the S&P 500, so committee decisions can materially influence demand and liquidity for would-be constituents (source: S&P Dow Jones Indices, S&P 500 benchmarked assets disclosures). Given MicroStrategy states it holds bitcoin as a primary treasury reserve asset, traders often treat MSTR as a high-beta proxy for BTC; exclusion means SPX-linked passive portfolios will not gain that direct BTC-sensitive exposure via MSTR (source: MicroStrategy Form 10-K and investor relations; S&P Dow Jones Indices methodology).