A wave of massive initial public offerings, including SpaceX, Anthropic and OpenAI, is set to hit US equity markets just as index providers move to fast-track their inclusion. Asset managers expect this combination could inject fresh volatility into passive investment strategies.
Last week, Elon Musk’s aerospace manufacturer SpaceX confidentially filed for an IPO and is targeting a June debut. The company is looking to raise 50 billion to 75 billion dollars at an estimated valuation of more than 1,500 billion dollars, with the potential to go higher depending on market conditions.
Nasdaq has already changed its rules to allow mega-cap IPOs to enter its Nasdaq 100 index within 15 trading days, instead of the standard three months. S&P Dow Jones Indices is consulting market participants on whether to follow suit for the S&P 500, a benchmark that underpins roughly 24,000 billion dollars in assets. That would force index-tracking funds to buy into some of the largest and most hyped companies in history almost immediately after listing.
“If large IPOs are added faster, index-tracking strategies can become mechanical buyers very soon after trading begins,” said Aegon AM portfolio managers Jacob Vijverberg and Jordy Hermanns. Fast-tracked inclusion could amplify both US concentration in global indices and short-term volatility. Passive investors are “likely to pick up that early volatility,” they told Investment Officer.
The SpaceX IPO would be the first of several extraordinarily large listings in 2026, with OpenAI and Anthropic also seen as potential candidates. Those IPOs would rank among the biggest ever and dwarf much of Europe’s equity market. Aegon estimates that passive funds linked to major US benchmarks could represent tens of billions of dollars in flows shortly after listing under a fast-track regime.
SpaceX valuation dwarfs Europe’s corporate elite
Fast entry
The rule changes mark a shift in how benchmarks are constructed. Traditionally, newly listed companies faced seasoning periods, allowing time for prices to stabilize and for more shares to become available for trading. The Nasdaq-100 requires a minimum free float of 10 percent, but the new rules waive this requirement for the largest companies.
Waiving those rules is a “bad idea,” said Owen Lamont, portfolio manager at Acadian Asset Management. He argues that fast-tracking large IPOs risks forcing index funds to buy into stocks before prices have properly formed.
With only a limited free float available at listing, early trading can produce inflated valuations that do not reflect underlying fundamentals. Cutting the waiting period to just days leaves little time for price discovery, especially when short selling is constrained and underwriters are still supporting the share price.
The result, Lamont argues, is that passive investors may systematically buy at elevated prices. Research on similar strategies shows that stocks often rise ahead of index entry and then decline afterward, leaving index funds exposed to losses.
MSCI and FTSE already operate fast-track mechanisms, though their inclusion criteria depend heavily on free float. For mega-cap IPOs, where only a limited portion of shares may initially be available, the timing and scale of index inclusion could still vary.
Private markets
Private markets have already absorbed large amounts of capital. Companies such as OpenAI have raised more than 100 billion dollars in private funding, reducing their reliance on public markets.
There are also signs of strong demand for exposure ahead of any listing. Investment vehicles holding stakes in private technology companies have traded at large premiums to their net asset value, while other listed companies with indirect ties have been used as proxy trades.
Even so, valuations remain difficult to assess. “For SpaceX, for example, we’re talking about multiples of 300 times earnings or something in that range, so there’s clearly a lot of hype or very strong expectations in those valuations,” said Hermanns.
Top-heavy index
Aegon’s analysis suggests that even conservative assumptions would push the US weighting in global benchmarks higher, while increasing exposure to technology and artificial intelligence sectors.
That would reinforce an existing trend. Global equity indices have become increasingly concentrated in a small number of large US technology companies. The addition of new mega-cap names would deepen that concentration and reduce diversification across regions and sectors.
While Europe continues to produce IPOs, they are smaller and concentrated in different sectors. The region lacks companies of the size currently seen in the US pipeline, limiting their impact on global benchmarks.
Still, Vijverberg highlights that market size does not automatically determine returns. Smaller or less concentrated markets can offer different risk-return profiles, underlining the continued role of diversification.