Interactive Brokers just got included in the S&P 500. Who is next to get the nod?

The S&P Dow Jones Indices announced Interactive Brokers will replace Walgreens Boots Alliance in the S&P 500 this Thursday, a move that historically sees newly added stocks gain 6-9% on average post-announcement. The upcoming third-quarter rebalance is anticipated to be more impactful, as it typically involves the year's largest turnover and more discretionary changes, contrasting with the unusual lack of adjustments in June. Analysts are speculating on potential significant additions, including MicroStrategy (a bitcoin/AI proxy), CRH, and Astera Labs, an AI connectivity chip firm that has already surged over 35% since its March IPO.

Analysis

The S&P 500 index is undergoing notable changes, creating distinct event-driven trading opportunities. S&P Dow Jones Indices has confirmed that Interactive Brokers (IBKR), which has already gained 42% year-to-date, will replace Walgreens Boots Alliance (WBA) in the index. This move is significant as historical data from Stephens indicates new additions typically outperform by an average of 6% to 9% the day after such an announcement, a pattern recently observed when Block (SQ) jumped approximately 7% upon its inclusion. The market's focus is now shifting to the more substantial third-quarter rebalance on September 5, which historically features the year's largest turnover, averaging 1.2%. This contrasts sharply with the static June rebalance, which negatively impacted speculative names like Robinhood (HOOD). Analyst speculation for the upcoming rebalance centers on three newly eligible companies: building products manufacturer CRH, bitcoin-proxy MicroStrategy (MSTR), and AI-chip firm Astera Labs (ALAB). The potential inclusion of MSTR is particularly noteworthy as it would follow other crypto-related firms into the index, signaling growing market acceptance, though its high beta and correlation to bitcoin make it a controversial choice. Meanwhile, Astera Labs has demonstrated strong momentum, soaring over 35% since its March IPO, highlighting investor appetite for AI-related exposures.

Key Decisions for Investors

• Investors seeking event-driven returns should monitor speculative S&P 500 candidates MicroStrategy (MSTR), CRH, and Astera Labs (ALAB) ahead of the September 5 rebalance, but must weigh the potential for an 'inclusion pop' against the risk of no change, as seen with Robinhood's decline after the Q2 rebalance.
• The confirmed inclusion of Interactive Brokers (IBKR) will generate mandatory buying from index-tracking funds, which could provide a further technical tailwind, though much of this may already be priced in following its 42% year-to-date rally.
• The potential addition of thematic stocks like MSTR (crypto) and ALAB (AI) serves as a key indicator of the index's evolving composition; their inclusion would validate these sectors and may warrant a portfolio review to ensure adequate exposure to these high-growth themes.