The blockbuster listings of SpaceX, Anthropic and OpenAI are set to prompt an unprecedented wave of buying and selling as new “fast entry” rules thrust the stocks straight into Wall Street indices.

The rules, implemented this month by Nasdaq, mean billions of dollars of passive money will automatically flow to the three companies shortly after they go public, driving their share prices higher but forcing investors to sell other stocks.

Elon Musk ‘s SpaceX filed for an initial public offering on Wednesday that is expected to be the largest on record, hours before OpenAI’s plans to list were revealed and rival Anthropic said it was on track to turn a profit, laying the groundwork for its own flotation.

SpaceX will make relatively few shares available to public investors at its IPO next month, a small “free float” which under old rules would exclude the rocket company from indices tracked by trillions of dollars of passive investments.

However, Nasdaq has loosened its rules as it battled to win the SpaceX listing over its rival NYSE, allowing the stock to join the Nasdaq 100 after just 15 days. SpaceX and other new entrants will also be given an index weighting equivalent to three times the value of the shares floated. S&P Dow Jones Indices is also consulting on changes that could fast-track the stock’s entry into the S&P 500.

The initial impact on the rest of the index will be limited by the relatively small number of shares on offer, but is likely to increase after a lock-up period expires, which will be staggered over the first 180 days of trading, according to the SpaceX prospectus.

JPMorgan estimates that if 50 per cent of the company’s shares are eventually floated with a valuation reaching US$2 trillion, passive investors would have to sell US$95 billion of Wall Street’s eight biggest existing tech stocks . The FT has previously reported that SpaceX is aiming for a US$1.75 trillion valuation.

“The SpaceX IPO, and the follow-on release of locked-up shares, [is] like no other single index event in recent history,” said Peter Haynes, head of index and market structure research at TD Securities, about the SpaceX listing. “We have been overwhelmed by institutional investors asking about the IPO, the name, the size, the impact.”

Investors are also bracing themselves for selling of smaller stocks that could be booted from indices later in the year to make way for SpaceX and other megacap arrivals.

Valérie Noël, head of trading at Syz Group, said that the “most discussed trades” in the market around the SpaceX listing included betting against “marginal Nasdaq 100 names”, which are candidates for index deletion, as well as pressure on the existing large-cap stocks.

Todd Sohn, chief ETF strategist at Strategas, said the small volume of available shares following the SpaceX listing means the index inclusion will feel “almost a little frantic, because you’re dealing with ETFs and passive products that are tracking trillions of dollars of assets and yet you only have five per cent of float available”.

The anticipated post-IPO pop in the share price could leave passive investors buying at a hefty valuation, according to Sohn. “If SpaceX is up 100 per cent the week after the IPO, and they have to buy it, they have to buy it. They have to take that price…They can’t discriminate,” he said.

The limited timeframe between the new listings and index inclusion means that “it is going to be noisy”, said Christian Raute, head of markets trading strategy at Citi. “Because it is so large, it is a challenge,” Raute said. “It might get expensive.”

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But ultimately, “the market is not going to have a problem absorbing these IPOs”, said Raute. “The whole industry is braced and has participants trained to deal with this.”

A portfolio manager at a large U.S. hedge fund said: “We’re going all in for maximum size on all of them [SpaceX, Anthropic and OpenAI]…We are not liquidity constrained at all.”

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