Anthropic, the artificial intelligence company behind the Claude chatbot, is expected to go public next week. But the early trading in its shares may have less to do with retail enthusiasm and more to do with the mechanical demands of index funds.
According to Reuters, investors are bracing for a debut that could be shaped by a newer playbook: major index providers have changed their inclusion rules so that large new listings can be added to key benchmarks within days, not weeks. That shift matters because passive index funds are required to buy a stock once it joins an index, regardless of the price they pay.
Why index funds could dominate early trading
For Anthropic, the mechanics are striking. Reuters reports that only about 6% of the company's outstanding shares are being offered in the IPO, leaving a relatively small pool of stock available for trading at first. That scarcity can amplify the impact of any large, forced buyer.
Research firm Intropic estimates that index-tracking demand could total roughly 28% of the IPO shares, or about $19 billion. Reuters adds that Anthropic could be added to at least six major indexes within 5 to 15 days of its debut. That timeline is much faster than the traditional quarterly review process, which could take months.
This isn't just a theoretical concern. When a stock is about to be added to an index, passive funds must buy it. Some hedge funds and other traders try to get ahead of that demand, buying early in hopes of selling to the index funds at a higher price. That front-running can push the stock up even before the official inclusion date.
The dynamic is similar to what happens with other newly listed companies that qualify for fast-track index inclusion. For example, MSCI's November review boosted India's weight in its emerging markets index, showing how index changes can move markets. And MSCI also removed some companies from major indexes, illustrating the flip side of forced selling.
Options trading and early supply
Options trading could add another, shorter-lived push. Market makers often hedge their positions by buying shares when options activity ramps up, which can create additional demand in the first days of trading.
But Reuters also flags potential early supply. Employees who own roughly 15% of the company's equity can sell on day one, and a separate $26 billion private sale reportedly has no lock-up. That means more shares could hit the market sooner than usual, potentially offsetting some of the index-driven buying.
For everyday investors, the key takeaway is that the first 5 to 15 days of Anthropic's trading may be driven by forced buyers, not fundamentals. The predictable bid from index funds could fade once the inclusion window closes, leaving the stock more sensitive to supply from employee sales and the private sale shares.
What it means for investors
For those considering buying Anthropic shares, it's important to understand that the early price may not reflect the company's long-term value. Instead, it could be a function of index fund mechanics and short-term trading strategies.
This is a common pattern with large IPOs that qualify for fast-track index inclusion. The initial pop can be followed by a pullback once the forced buying ends. Investors who buy at the peak of that forced demand could face losses if the stock reverts to a more fundamentals-driven price.
That said, the AI sector has been a major driver of market gains, and Anthropic's IPO buzz has already lifted chip ETFs. The company's technology is widely used, and its valuation will be closely watched as a barometer for AI sentiment.
Retail traders are also expected to participate. Vanda Research estimates retail investors could pour $250 million into the IPO, adding to the early demand.
But the bigger force may be the index funds. As Reuters notes, the inclusion rules have changed, and that means the market for Anthropic's shares could be more mechanical than emotional in the first few weeks.
For now, investors should watch the IPO pricing, the first day of trading, and the timing of index inclusion announcements. Those factors, more than any single piece of news, are likely to determine the stock's early trajectory.
In the end, Anthropic's IPO is a reminder that in today's markets, passive money can be just as powerful as hype. Understanding that dynamic is key to making informed decisions.
