Most people know they own index funds. Very few know the rules governing what goes into those indexes. This week those rules changed for millions of Americans. Cook Pierce explains what to look for and why it matters.
Do you know which specific indexes your retirement funds track and what the rules are for what goes into them?
Most people know they own index funds. Very few know the specific indexes those funds track or the rules governing what companies enter and exit those indexes.
This week that gap became consequential.
Not all index funds are the same. The companies inside them, the rules governing which companies qualify and the thresholds for inclusion vary significantly across the major indexes.
The S&P 500 tracks 500 large American companies. To qualify a company must have traded publicly for at least 12 months, maintain a minimum public float and demonstrate four consecutive quarters of positive net income. SpaceX, which lost $4.9 billion last year, does not qualify. It will not be eligible until at least mid-2027.
The Nasdaq-100 tracks the 100 largest non-financial companies listed on the Nasdaq exchange. This week Nasdaq changed its rules to allow large newly public companies to enter the index within 15 days of their IPO. SpaceX will enter the Nasdaq-100 approximately two weeks after it goes public.
FTSE Russell changed its rules similarly. Morningstar CRSP dropped its minimum float requirement to accommodate SpaceX and other large IPOs. MSCI and FTSE Global already had fast-track provisions.
The rules are different. The exposures are different. The risk profiles are different. And most passive investors do not know which of these indexes their retirement funds are tracking.
Your fund's name often contains a clue. A fund described as an S&P 500 index fund tracks the S&P 500. A fund described as a total market fund or a growth fund may track something broader or different.
The most reliable way is to look up your fund's prospectus or fact sheet, which every fund is required to publish. It will state clearly which index the fund tracks. Your brokerage or plan administrator can also tell you.
The key question to ask is: which index does this fund track and what are the eligibility rules for that index?
Index eligibility rules have historically been stable, technical and rarely newsworthy. This week they became something else.
Nasdaq changed its rules specifically to accommodate SpaceX's preference for fast index inclusion. The exchange had commercial reasons to do so. Larger, more valuable companies in the index increase the index's relevance and the demand for funds that track it. The decision was made by an exchange, not by the investors whose retirement accounts will now hold SpaceX shares.
The S&P 500's refusal to change its rules is meaningful precisely because of this context. It chose institutional integrity over commercial pressure. That choice protects the millions of Americans whose retirement funds track the S&P 500 from this week's exposure.
Whether that protection remains in place as the commercial pressure grows is a question worth monitoring.
If your retirement funds track the S&P 500 primarily, SpaceX is not in your account yet and will not be for at least a year under current rules.
If your retirement funds track the Nasdaq-100 or other indexes that changed their rules this week, SpaceX will be in your account within weeks whether you want it or not.
If you do not know which indexes your funds track, this week is a good reason to find out.
The passive investor in 2026 is navigating index rule changes, political risk around AI equity stakes and legislative proposals that could cut AI stock values in half overnight. None of these decisions are being made by the investor. All of them affect the investor's retirement account.
Knowing which indexes your funds track is not active investing. It is the minimum awareness that passive investing now requires.
