On June 12, 2026, SpaceX completed the largest initial public offering on record, raising approximately $75 billion at an implied valuation near $1.8 trillion. Fifteen trading days later, on July 7, the company entered the Nasdaq-100. In the span of a few weeks, tens of millions of Americans who hold index funds became SpaceX shareholders, whether or not they set out to be.
SpaceX may be the opening act. Anthropic filed a confidential registration statement with the SEC on June 1, 2026, and reports suggest it could list as early as the fourth quarter. OpenAI filed roughly a week later, though recent reporting indicates it may wait until 2027. Together, these three companies represent several trillion dollars of market value that, until this summer, sat entirely outside public benchmarks.
For investors who hold passive index exposure, a practical question follows: when companies of this scale move from private markets into public benchmarks, what actually changes, and where? The answer depends heavily on which index you own, because each major benchmark is built on different rules.
Three Indexes, Three Rulebooks
Index investing is often described as passive, and while the indexes themselves are not
neutral, they are designed to track a specific market index. Each reflects a set of construction decisions that determine which companies enter, when they enter, and how much they weigh.
The Nasdaq-100 tracks approximately 100 of the largest non-financial companies listed on the Nasdaq exchange, using a modified market capitalization weighting. In May 2026, Nasdaq adopted a fast-track framework that allows large newly public companies to join on their fifteenth trading day, provided they rank among the 40 largest eligible Nasdaq-listed companies. SpaceX is the first mega-IPO admitted under this rule.
The S&P 500 is governed by a committee and applies stricter gates: roughly twelve months of trading history, positive GAAP earnings over the trailing four quarters (including the current quarter), and minimum float requirements.
The Russell 1000 and Russell 3000 are rules-based and broad, reconstituted annually with quarterly additions for eligible IPOs, capturing roughly the 1,000 and 3,000 largest U.S. companies respectively.
Same company, three different outcomes.
The Nasdaq-100: Where the Effect Concentrates
SpaceX’s July 7 addition triggers mechanical buying from every fund tracking the index, a pool of assets exceeding $800 billion globally. Analysts have estimated that passive inclusion flows could approach $4.3 billion.
Two features of the inclusion deserve attention.
First, the initial weight is smaller than the headline valuation may suggest. Because index weights reflect float-adjusted market capitalization, and because a relatively small share of SpaceX stock trades publicly, early estimates place the company’s initial weight between roughly 0.5% and 1% of the index. This figure may rise as lockup periods expire and float
expands over the coming quarters. The staggered lockup schedule begins releasing insider shares after second-quarter earnings, which could arrive as early as mid-July.
Second, the character of the index shifts. SpaceX brings exposure to launch infrastructure, satellite communications through Starlink, and, following its February 2026 combination with xAI, frontier AI development. The Nasdaq-100 was already concentrated in mega-cap growth; this addition deepens that orientation.
The implication cuts both ways. If SpaceX shares appreciate, Nasdaq-100 investors may
potentially participate more fully than holders of broader benchmarks. If the valuation compresses, the index carries proportionally more of that drawdown. At its IPO, SpaceX priced at roughly 94 times trailing 2025 revenue of $18.7 billion, while remaining unprofitable on a GAAP basis with a cumulative deficit exceeding $41 billion since its founding. Shares surged to $225 in the days after the debut before retreating roughly 28% from that high. Valuation risk of this magnitude, imported directly into a core index holding, is worth understanding rather than assuming away.
History offers a note of caution on inclusion itself. Palantir and Strategy both joined the Nasdaq-100 in December 2024, and both peaked around or shortly before their inclusion dates. Index membership has historically functioned as a milestone, not a catalyst.
The S&P 500: The Waiting Room
Contrary to some early commentary, SpaceX does not currently qualify for the S&P 500. The profitability requirement matters here: the company reported a multibillion-dollar GAAP loss for 2025 and has cautioned investors that it may not achieve profitability. Combined with the seasoning requirement, S&P 500 inclusion appears to be a 2027 question at the earliest, and it is contingent on financial results that have not yet materialized.
If and when inclusion occurs, the effect would likely be meaningful but diluted. A single constituent among 500, even a large one, moves the S&P 500 far less than the same constituent moves a 100-stock index. A 20% move in SpaceX would register in the S&P 500, but at a fraction of its influence on the Nasdaq-100.
This asymmetry is itself informative. Investors holding S&P 500 funds have a buffer, both in breadth and in the index’s quality gates, that Nasdaq-100 holders do not.
The Russell Indexes: Breadth as Buffer
SpaceX qualifies for Russell inclusion through the standard IPO addition process, with estimates of roughly $3 billion in associated passive demand. Across 1,000 or 3,000 constituents, however, the incremental effect on returns is modest. The primary consequence is a further tilt toward mega-cap growth within indexes that were already drifting in that direction.
In rough order of sensitivity to SpaceX’s performance: the Nasdaq-100 sits at the high end, the S&P 500 in the middle once inclusion occurs, and the Russell 1000 and 3000 at the low end.
The AI Listings Behind It
The more consequential story may be what comes next. Anthropic’s last private round in May 2026 valued the company near $965 billion. OpenAI has been valued at around $1 trillion. Under the Nasdaq fast-track framework, either company could enter the Nasdaq-100 within weeks of listing, just as SpaceX did.
Should both listings proceed, the cumulative effect on benchmark composition could be substantial: three of the largest constituents in growth-oriented indexes would be recently public, capital-intensive companies whose valuations rest on long-duration growth expectations rather than current earnings. Growth indexes become more growth-oriented. Value benchmarks are subject to changes. Large-cap growth managers acquire significant incidental exposure whether they underwrite these businesses or not.
What This May Mean for Your Portfolio
A few considerations emerge for investors with meaningful index exposure.
Passive is a set of active decisions. Index rule changes, like Nasdaq’s fast-track framework, alter what you own without any action on your part. Understanding the construction rules behind your benchmarks has become more important, not less.
Concentration deserves monitoring. Mega-cap concentration in growth indexes was already elevated before this IPO wave. Investors may wish to review how much of their equity allocation is effectively a bet on a narrow set of long-duration growth stories.
Rebalancing discipline can matter more in concentrated regimes. When a handful of names drive index returns, systematic rebalancing may help manage the risk that recent gains embed into outsized position sizes.
Taxable investors face additional wrinkles. Index reconstitution events generate turnover, and for taxable portfolios, approaches such as direct indexing may offer more control over how these transitions are realized.
None of this argues for abandoning index exposure. It argues for understanding it. The indexes of 2027 may look materially different from the indexes of 2024, and that difference is being written now, one fast-tracked inclusion at a time.
If you would like to discuss how index construction changes may affect your portfolio, we welcome the conversation.
This material is provided for informational and educational purposes and does not constitute investment, legal, or tax advice, nor an offer or solicitation to buy or sell any security. References to specific companies and indexes are for illustration and do not constitute recommendations. Market data reflects publicly reported figures as of July 2026 and is subject to change. Past performance is not indicative of future results. Investing involves risk, including possible loss of principal. Certuity, LLC is a registered investment adviser. Registration does not imply a certain level of skill or training.