The planned IPO of SpaceX is increasingly being viewed not simply as another blockbuster listing, but as a structural event that could reshape how modern index investing influences stock prices.
Leading that argument is veteran index strategist Rob Arnott, whose research over decades has often challenged conventional assumptions about passive investing and benchmark inclusion.
Arnott believes SpaceX may defy the historical pattern that typically sees newly added index constituents underperform after inclusion. Instead, he argues the Elon Musk-led company could experience extraordinary upward pressure because of a unique combination of limited public float, accelerated index eligibility, and massive forced demand from passive investment vehicles.
Register for Tekedia Mini-MBA edition 20 (June 8 – Sept 5, 2026).
Register for Tekedia AI in Business Masterclass.
Join Tekedia Capital Syndicate and co-invest in great global startups.
Register for Tekedia AI Lab.
The mechanics matter because SpaceX is reportedly targeting a valuation near $2 trillion while selling roughly $75 billion worth of shares in its IPO. That implies only about 3.75% of the company would initially trade publicly, an unusually small float for a company of that scale.
Ordinarily, such a low float might have delayed inclusion into major indexes. But recent rule changes by Nasdaq significantly altered the equation. Before May 1, companies generally needed a public float of at least 10% to qualify for inclusion in the Nasdaq 100. Under the revised framework, that threshold effectively disappears for firms ranking among the exchange’s 40 largest stocks.
That change could allow SpaceX to enter the Nasdaq 100 just 15 trading days after listing, dramatically accelerating demand from ETFs and institutional portfolios benchmarked to the index. The company would then likely become eligible for the S&P 500 roughly six months later, potentially unleashing another wave of compulsory buying from trillions of dollars tied to S&P-linked passive products.
Arnott told Business Insider’s William Edward that sequence creates a powerful supply-demand imbalance rarely seen in public markets.
“I would say that the buying pressure will be overwhelming,” he said.
His view is rooted in the structural dynamics of passive investing, which now dominates large portions of U.S. equity ownership. Index funds and ETFs do not evaluate whether a stock is cheap or expensive before purchasing shares. They buy because benchmark rules require them to.
That creates what Arnott and other critics of passive investing describe as “price-insensitive demand.”
In SpaceX’s case, the effect could be amplified because there may simply not be enough freely traded shares available to satisfy institutional demand once index inclusion begins. The result, according to Arnott, could resemble a prolonged scarcity premium where the stock continues climbing as passive funds compete for a limited supply of shares.
The phenomenon would also expose a growing tension inside modern financial markets: indexes increasingly shape prices rather than merely tracking them.
Passive investing has exploded over the past decade, with trillions of dollars flowing into benchmark-linked products managed by firms such as BlackRock, Vanguard, and State Street Global Advisors. That growth has transformed index inclusion from an administrative event into a major market catalyst.
Historically, stocks added to indexes often rallied sharply ahead of inclusion because traders anticipated forced buying by passive funds. However, Arnott’s research has shown that many newly added stocks later underperform once that initial demand wave fades.
SpaceX, he argues, may be different because of its unusually constrained float and the likelihood that additional insider shares could gradually enter the market over time, forcing indexes to continuously increase the company’s weighting.
That would create recurring mandatory purchases by index-tracking funds.
The situation also highlights how elite private companies are increasingly arriving on public markets, already operating at immense scale. SpaceX would likely debut as one of the largest publicly traded companies in the world immediately upon listing, bypassing the traditional gradual growth path that historically characterized IPOs.
The company’s dominant position in commercial launches, satellite internet through Starlink, and U.S. government space contracts has already made it one of the most closely watched private firms globally. Its IPO is expected to attract extraordinary retail and institutional interest, particularly given founder Elon Musk’s ability to command investor attention and drive speculative momentum.
Still, even bullish analysts acknowledge risks remain substantial.
SpaceX’s valuation assumptions already imply enormous future growth expectations. Any slowdown in satellite revenue expansion, launch cadence, government contracts, or profitability could pressure the stock regardless of indexing dynamics. Macroeconomic conditions may also matter. Rising interest rates, geopolitical tensions, or a broader market correction could weaken investor appetite for high-valuation technology companies.
Yet Arnott believes the underlying market structure itself may overpower many traditional valuation concerns, at least initially.
The broader implication is that modern equity markets are increasingly influenced not just by fundamentals, but by the plumbing of passive capital flows, benchmark methodologies, and liquidity mechanics. For critics of passive investing, SpaceX could become the clearest example yet of how index construction rules now have the power to move trillions of dollars and materially reshape stock prices independent of conventional valuation analysis.