Can the stock market swallow SpaceX, Anthropic and OpenAI?

THEY promise to be the biggest stock-market debuts in history. On Thursday (Jun 11), SpaceX reportedly hopes to raise US$75 billion from investors by issuing shares that will begin trading on the Nasdaq exchange the next day.

Elon Musk’s rocketry firm will probably soon be followed by two other mammoth listings.

Anthropic, an artificial-intelligence lab, filed draft paperwork for its initial public offering on Jun 1. OpenAI, a competitor, is expected to do so soon.

The two are rumoured to be seeking as much as US$60 billion apiece. Together, the three giga-IPOs may add as much as US$4 trillion to the market value of listed American companies in a matter of months.

How on earth will the stock market handle this? Headlines predict a “trading frenzy”. Steve Sosnick, chief strategist at Interactive Brokers, one of the world’s biggest online trading platforms, has warned of the “existential risk” the listings pose.

A particular worry is that compilers of stock-market indices will grant the gigantic trio fast-track entry to their benchmarks. That would prompt tracker funds with trillions of dollars in assets to buy the newly minted shares days after they are issued. After exhausting a big pool of buyers straight away, who will be left?

The answer is – lots of investors in an extraordinarily deep and liquid market. Unprecedented as the serving of supersized IPOs is, America’s extraordinary stock market will gulp it down.

In the years to follow, though, expect some indigestion.

Just a rounding error

First, put the giga-IPOs’ size in context. In nominal terms, the record for capital raised by a debut listing is held by Saudi Aramco, which in 2019 pulled in US$29 billion (US$38 billion in today’s money) when it floated in Riyadh.

SpaceX, Anthropic and OpenAI are collectively targeting US$200 billion-odd. Yet, this is a rounding error in America’s bourses. Firms in the broad Russell 3000 share index have a total market value of US$77 trillion; those in the narrower (but more widely tracked) S&P 500 index of big companies are worth US$65 trillion.

Therefore, investors in index funds will not immediately see their portfolios change much.

Although Nasdaq has already shortened the “seasoning” period before index inclusion to 15 trading days and FTSE Russell has slashed its waiting time to five days – with S&P Dow Jones reportedly considering something similar – most share indices weight firms in proportion to the value only of shares they have released for public trading, or the “free float”.

For SpaceX, this means just the US$75 billion or so of stock it intends to issue in June – so its initial weight in the S&P 500 will be around 0.1 per cent.

The Nasdaq 100 is an exception, and has changed its rules to weight companies at up to three times their free float, in an apparent effort to woo Musk. Even so, SpaceX’s probable initial weight in this US$40 trillion index will be only around 0.5 per cent.

Whatever floats your starship

This will change as more shares are released for trading. All of America’s listed tech giants have free floats above 85 per cent; the lowest is that of Meta, which went public in 2012 and has 13 per cent of its shares still owned by Mark Zuckerberg, its founder.

At first, “lock-up” provisions in the IPO prospectuses of SpaceX, Anthropic and OpenAI will prevent company insiders and early investors from selling their existing stakes and raising the free float.

Over time, however, these will expire and trillions of dollars’ worth of new shares will come to market.

SpaceX plans to release its locked-up shares in a series of tranches. If its IPO issues US$75 billion of shares, valuing the firm at its hoped-for US$1.8 trillion, the initial free float will be 4 per cent.

None of Musk’s stake, which accounts for about half of the remainder, can be sold for 366 days after the IPO. This restriction also applies to some shares held by “certain significant investors”.

Lock-ups on the rest, representing a little under half of SpaceX’s value, will expire more quickly. After its first quarterly report, probably in August or September, insiders can sell 20 per cent of their stakes. They can offload another 10 per cent if the shares are then trading 30 per cent or more above their IPO price.

Extra tranches are due for release on set dates after the IPO, and after the second quarterly earnings report.

Insiders do not have to sell their shares, of course. Musk, in particular, may hold on to his – most of which carry outsize voting rights and so cement his control of SpaceX.

Similar considerations will apply to shareholders in Anthropic and OpenAI after the labs’ flotations. So the addition of these firms to public markets will unfold over years rather than days.

Potential post-IPO disappointment

Gradual does not, however, mean inconsequential. If history is a guide, those who buy the resulting shares stand a good chance of disappointment.

Jay Ritter of the University of Florida has studied the post-IPO returns of stocks listed between 1980 and 2024. The average such stock returned 20 percentage points less than the broader market over the three years after its first trading day.

Firms valued at more than 40 times their revenue underperformed by 58 percentage points. SpaceX, with a valuation of US$1.8 trillion, would begin trading at over 90 times its revenue.

Blockbuster IPOs are also often taken as a sign that a bull market is nearing its peak – understandably, since firms want to sell shares for top dollar.

The last surge in listings, in 2020 and 2021, came just before a bear market. Previous IPO booms, for instance in the late 1990s or the years before 2008, were followed by far-bigger slumps.

Today, if the giga-trio underperforms, it may even precipitate a stock-market rout. All three firms are closely associated with progress in AI and so too, increasingly, is the wider market: America’s 10 biggest listed AI-related firms already account for two-fifths of the S&P 500’s value.

Bad news for SpaceX alone might not harm a tracker fund much; bad news for AI certainly would.

Funds that weight each of an index’s component stocks equally, rather than by market value, offer some protection from this. But they also amount to betting against the market – the opposite of passive investment.

A broader worry still is that the giga-IPOs herald more capital-raising, both by the newly listed tech giants and their older peers.

For years, notes Victor Haghani of Elm Wealth, an investment firm, capital has been abundant and shares increasingly scarce. Tech giants have generated so much cash that they have been buying back shares rather than issuing new ones at the same time as white-collar workers have ploughed retirement savings into the market.

This has driven up share prices.

Now the tech behemoths are slowing share buy-backs or halting them altogether, instead reinvesting their profits to develop AI.

Several have turned to the bond market for more capital. Alphabet, Google’s corporate parent, said previously that it would issue US$85 billion in new shares. And the club’s newest members are tapping the stock market.

Simultaneously, white-collar workers are perhaps most in danger of seeing AI automate their jobs and immiserate their pension pots. Expect investors to go gaga for the giga-IPOs.

A few years from now, though, the stock market may need to prepare for a capital diet. ©2026 The Economist Newspaper Limited. All rights reserved