Anthropic's planned IPO aims for a $2 trillion valuation and could become the largest in history. But with most IPOs lagging after their debut and S&P 500 rules delaying index inclusion, investors face real risks and volatility
Anthropic's upcoming IPO will test the market's demand for artificial intelligence stocks at a time when AI-driven gains have dominated the S&P 500. With backers targeting a $2 trillion valuation, the offering could surpass Space Exploration Technologies as the largest IPO ever attempted. However, the transition from a high-profile debut to long-term stability is rarely straightforward, and the implications for both individual investors and index funds are significant.
Reuters reports that Anthropic has chosen Nasdaq as the venue for its potential IPO, though the deal is not yet finalized and key terms remain under negotiation. The company may begin marketing the offering no earlier than mid-October 2026, with the listing expected to close before the U.S. midterm elections in November, but the timeline is still subject to change. Reuters reporting also notes that the IPO could raise up to $100 billion, making it the largest in history if current parameters are met.
Nvidia is in talks to become a cornerstone investor in Anthropic's IPO and could invest up to $10 billion, according to Reuters.
Unlike some recent mega-cap listings, Anthropic will not be fast-tracked into the S&P 500. The index requires a full year of public trading, at least 10% of shares in public hands, and positive earnings under generally accepted accounting principles. Even SpaceX, which joined the Nasdaq-100 within weeks of its own IPO, remains outside the S&P 500. For Anthropic, the earliest possible inclusion would be late 2027 if the IPO proceeds as planned in late 2026.
IPO Performance and Market Risks
Historical data offers a cautionary perspective for those expecting immediate gains from high-profile IPOs. Research covering more than 9,000 U.S. IPOs from 1980 to 2025 shows an average first-day gain of 19%. However, IPOs from 2012 to 2024 underperformed the broader market by an average of 25.5% over the following three years. SpaceX's post-IPO performance illustrates this volatility: after pricing at $135, its shares rose to $225.64, then fell to $104.83, before recovering to $151.10 by September 16. Such fluctuations can challenge even experienced investors' risk tolerance and patience.
Anthropic's IPO will also serve as a gauge for the broader AI sector. As detailed in a Reuters financial review, AI stocks accounted for more than 80% of the S&P 500's gains through mid-May 2026. If Anthropic's debut attracts limited demand, it could indicate waning enthusiasm for AI exposure, with potential consequences for funds and portfolios heavily weighted toward the sector.
S&P Dow Jones Indices requires companies to have at least 12 months of public trading history, a minimum of 10% of shares in public float, and positive GAAP earnings before they can be included in the S&P 500. This policy explains why even the largest IPOs are not added to the index immediately after listing.
Even before Anthropic's shares become eligible for S&P 500 inclusion, many index fund investors already have indirect exposure. Amazon and Alphabet, two of the index's largest components, hold significant stakes in Anthropic. Amazon alone reported $16.8 billion in pretax gains from its Anthropic position in the first quarter of 2026. A strong IPO could increase the value of these holdings, while a weak debut could negatively affect their performance.
For index funds tracking the S&P 500, the rules are explicit: they must purchase stocks only after they are added to the index. S&P Dow Jones Indices reaffirmed its requirements for mega-cap IPOs as recently as June 4, maintaining the 12-month public trading rule and other criteria. As a result, even if Anthropic's IPO is highly successful, index funds will not be immediate buyers, and the stock's price could remain volatile until eventual inclusion in the index.
Lessons from Recent AI Stock Surges
Anthropic's IPO arrives as AI valuations face increased scrutiny. As previously reported, the rapid rise in AI stock prices has raised questions about sustainability, particularly as inflation and historical tech bubble patterns influence investor sentiment. The performance of Anthropic's shares after the IPO will be closely monitored as an indicator of whether the AI rally can persist or if the market is approaching saturation.
For investors considering participation, it is important to recognize that IPOs often deliver their largest gains on the first day, followed by years of underperformance relative to the market. The experience of SpaceX and the broader IPO market underscores the need for patience and a clear understanding of risk. Anthropic's transition from private company to public entity will test both its business model and investors' willingness to pay a premium for AI exposure.
IPO investing involves unique risks distinct from those of established stocks. New listings can experience significant volatility, limited public information, and unpredictable trading patterns. Index inclusion may eventually provide price support, but only after a company meets strict eligibility criteria. For those seeking AI exposure, indirect routes through established index components like Amazon and Alphabet may offer a more stable approach, though these come with their own risks and dependencies. Understanding the mechanics of IPOs, index fund rules, and sector concentration is essential for navigating the next phase of AI-driven market developments.
