Anthropic, OpenAI and SpaceX IPOs Threaten Market Liquidity

Anthropic confidentially filed for an initial public offering and did not disclose size or timing. The filing keeps the company on track to list as early as this fall. SpaceX is expected to begin trading in the coming days and OpenAI is widely expected to file for an IPO soon. Combined, the three listings are projected to create about $200 billion in new public equity supply.

If any of the companies debut at or above recent private valuations, they would rank among the largest companies by market value once included in major indices, surpassing some established S&P 500 constituents. S&P Dow Jones Indices has opened a consultation on possible rule changes that could shorten waiting periods and adjust profitability requirements for very large companies, which would affect the timing of index inclusion.

Jean Fusshoeller, a portfolio manager at Capital at Work, warned that inclusion in major indices is not automatic and that expectations of mechanical buying by passive funds can move prices ahead of actual index decisions.

Institutional cash allocations are unusually low. Bank of America data show fund managers’ cash levels below 4%, the lowest since February 2024, leaving many funds near fully deployed. Brokers have invited clients to participate in the SpaceX offering. Television host Jim Cramer posted on the social platform X questioning what would have to be sold to raise hundreds of billions of dollars.

Ed Yardeni, president of Yardeni Research, argued that concerns about an immediate liquidity drain are overstated. He pointed to the U.S. market’s size — a Wilshire 5000 market capitalization near $75.6 trillion and an S&P 500 around $60 trillion — and to recent equity issuance totals of roughly $232 billion over the past year and more than $450 billion in 2021. Yardeni also noted that retail investors may participate in the offerings.

Public supply is likely to start small. SpaceX is expected to float about 4.3% of its shares at IPO, and Anthropic and OpenAI are also expected to begin with limited free floats as lock-up agreements restrict insider sales. Yardeni’s estimates indicate that S&P 500 index funds alone could absorb nearly one-fifth of SpaceX’s public float within six months, with Nasdaq-100 and Russell 1000 funds taking another 24 percent. Limited public supply combined with forced buying by index trackers could produce pronounced price moves while insider lock-ups remain in effect; supply is expected to increase gradually as those restrictions expire.

Historical data show many IPOs underperform after listing. Research covering 1980 through 2024 by University of Florida finance professor Jay Ritter found the average IPO underperformed the broader market by about 20 percentage points over the three years following listing. Firms priced at more than 40 times revenue underperformed by roughly 58 percentage points over the same period. Recent private-market valuations place SpaceX at above 90 times revenue.

Corporate equity activity beyond the three companies may add to investor demand for capital. Alphabet announced plans for up to $80 billion in equity issuance to fund AI computing infrastructure, including $30 billion in concurrent underwritten offerings (split between mandatory convertible preferred stock and common equity), a $10 billion private placement to Berkshire Hathaway, and a $40 billion at-the-market program beginning in the third quarter of 2026.

Broker invitations and retail interest indicate demand, but timing, allocation and index inclusion rules remain unresolved. Filings, trading starts and index decisions in the coming months will determine how and when the new supply is absorbed by public markets.