The recent stock market debut of SpaceX has presented a significant dilemma for major index providers. They must choose between adhering to strict inclusion criteria or modifying their rules to reflect the current market landscape, as these two objectives often conflict.

Financial advisors and asset managers acknowledge that both approaches can serve investor interests. However, balancing this conflict requires careful consideration of the risk tolerance and volatility assumptions embedded within index rules. Historically, index investing has often been marketed as a standardized, one-size-fits-all solution.

Dina Ting, Head of Global Index Portfolio Management at Franklin Templeton, commented, "The IPO is just the surface-level event. The core issue lies in index construction methodology. Investors must pay attention to this, as the assets you ultimately hold depend entirely on which index you track."

Investors and index professionals note that SpaceX's listing may herald a wave of large-scale IPOs, with other prominent AI firms like Anthropic and OpenAI potentially following this year. This trend is prompting the market to reassess which types of indices best align with their desired risk-return profiles.

Currently, the Nasdaq has decided to quickly include SpaceX in its flagship Nasdaq 100 index. In contrast, S&P Dow Jones Indices, which compiles the benchmark S&P 500, has opted to delay inclusion. These contrasting approaches reinforce the Nasdaq's reputation as suitable for investors willing to tolerate significant stock price volatility in pursuit of higher returns.

Joel Schneider, Deputy Head of Portfolio Management at Dimensional Fund Advisors, stated, "Each index makes its own adjustments regarding the timing and weighting of stock inclusions, leading to vastly different experiences for end investors. Our firm's investment philosophy centers on moving beyond traditional index investing."

Schneider added that this wave of major IPOs is "prompting financial advisors and individual investors to start paying closer attention to index construction rules, their underlying logic, and their market impact."

Competition for Mainstream Index Inclusion

Months before its listing, SpaceX actively sought inclusion in two core indices: the broad U.S. market benchmark S&P 500 and the Nasdaq 100, which has long aggregated leading U.S. technology firms.

Investors gain broad exposure by purchasing mutual funds and ETFs that track these indices, such as the Invesco QQQ ETF tracking the Nasdaq 100 and the State Street SPDR S&P 500 ETF (SPY).

Eric Kuby, Chief Investment Officer at North Star Investment Management, noted, "For years, investors with higher risk appetites have been shifting from S&P 500 products to QQQ. The differing inclusion decisions by index providers this time will likely accelerate that trend further."

The Nasdaq modified its rules to allow for SpaceX's rapid inclusion within a month of listing, returning to its original mission of supporting high-growth companies, even if some are not yet consistently profitable. If Anthropic and OpenAI also list on the Nasdaq, it could echo the phenomenon seen during the 2000 dot-com bubble, where valuations severely detached from fundamentals.

Large IPOs: Risks Beneath the Spotlight

If trillion-dollar index funds tracking the S&P 500 were to change their rules to include SpaceX, they would be forced to make massive passive purchases of the stock. The three largest S&P 500 tracking ETFs (from Vanguard, Invesco, and State Street) collectively manage around $3.2 trillion in assets. In comparison, the leading Nasdaq 100 funds have a total size of only about $600 billion.

The S&P 500's delay in including SpaceX and similar newly listed companies could lead to a significant divergence in performance between the two major indices, potentially reaching new highs in recent years. Investors find themselves torn between the allure of hot new AI-related listings and concerns over the high risks associated with trillion-dollar valuations.

King Lip, Chief Strategist at Baker Avenue Wealth Management in San Francisco, said, "Overall, investors with a higher risk tolerance are better suited for the Nasdaq 100, an index that can accommodate unprofitable growth companies. If market risk aversion increases, the S&P 500 will likely outperform on a comprehensive basis."

Schneider cited academic research published this month in the Review of Asset Pricing Studies, which found that IPO stocks taking the fast-track inclusion route can achieve up to a 5-percentage-point excess return relative to ordinary new listings before official inclusion. However, more than half of those gains are typically erased within two weeks of inclusion.

It is undeniable that funds tracking the S&P 500 remain heavily invested in technology stocks and are deeply tied to the AI-driven rally lifting the broader market. In the eyes of some investors, this also implies increased portfolio vulnerability.

Noted short-seller Jim Chanos stated, "The rapid inclusion of some new stocks into indices is a new market development. Long-term passive investors will see the risk level of their holdings significantly higher than historical averages. The systemic issue of this AI bull market is essentially a substantial increase in risk across the entire market's stock portfolio." He had previously warned that SpaceX's listing valuation is entirely supported by market optimism, with fundamentals unable to justify the current stock price.