The Nasdaq gives a green light to SpaceX’s inclusion, but the S&P 500 keeps it out? — Unpacking the methodology behind index construction
- Core thesis: Using the cases of SpaceX and Coinbase being included in different indices, this article dissects the four core methodologies of index construction (selection, weighting, calculation, and review). It also reveals the mechanisms by which index inclusion affects stock prices, emphasizing that the signaling effect of index inclusion matters more than the short-term impact of passive fund buying.
- Key elements:
- The three major index systems diverge significantly on SpaceX's admission rules: the Nasdaq-100 allows its inclusion through the "15-trading-day fast track" rule, while the S&P 500 adheres to the hard profitability threshold of "four consecutive quarters of positive GAAP net income," meaning SpaceX may not be eligible until as late as 2027.
- Index construction methodology comprises four publicly disclosed components: selection (stock criteria), weighting (impact measurement), calculation (point conversion), and review (periodic rebalancing). The transparency of methodology is the cornerstone of an index's credibility and a prerequisite for fund companies to license it for developing ETFs.
- The S&P 500 uses float-adjusted market-cap weighting with a profitability threshold. In May 2025, Coinbase qualified for inclusion after posting $65.6 million in Q1 net income, becoming the first crypto company to join the index. During the same period, MicroStrategy was excluded due to a $4.2 billion GAAP net loss.
- Price volatility triggered by index changes is often misread: for example, Reddit rose 15% after hours following its inclusion announcement, but a significant portion of that gain was driven by "short covering" — with 13% of the free float sold short — and front-running by active funds, unrelated to passive fund buying.
- An empirical study by the New York Fed covering 1989–2009 data points out that the "S&P 500 index effect" largely reflects a continuation of "strong stay strong" momentum, rather than inclusion itself creating long-term value out of thin air.
On July 7, 2026, SpaceX joined the Nasdaq-100 under the newly revised "15 trading day fast-track" rule; however, the S&P Dow Jones Indices Committee, after a public market consultation, issued a notice rejecting any proposal to create a fast track for SpaceX, insisting on the hard criterion of "positive GAAP net income for four consecutive quarters." This means SpaceX may not truly enter the S&P 500 until 2027 at the earliest. For the same company, the three major index systems—S&P 500, Nasdaq-100, and FTSE Russell—gave three completely different timelines. How exactly are indices compiled? What kind of companies can be added to an index? And why does the market always experience noticeable volatility when index constituents change? The following series of special features on indices and ETFs will peel back the layers of passive investing step by step.
SpaceX's "selection Rashomon" is not fundamentally a divergence in market sentiment, but rather a difference in the admission rules set by the three index systems—Nasdaq-100 greenlighted the company under its newly revised rules, while the S&P 500's hard profitability threshold hit the pause button. To truly understand what lies beneath such headline news, and to grasp the opportunities and risks that every future index rebalancing may bring, the first indispensable lesson is to understand the methodology of index construction itself: What components does it consist of? And who decides whether a company qualifies for inclusion, and when?
Is Index Construction Methodology the Core Trade Secret?
An index is, at its core, a product that requires "credibility." To be recognized by the market and to have fund companies willing to pay for licenses to develop ETFs tracking it, an index must possess credibility. The construction methodologies of mainstream indices are all publicly available materials, subject to public oversight and scrutiny! This is precisely why institutions like S&P Dow Jones Indices, Nasdaq, and FTSE Russell have come to dominate the space—their stock selection rules are transparent, deeply rooted in history, and their sample representativeness has been repeatedly validated by the market. Before selecting an ETF, the first thing to confirm is never how much the fund has gained in the past, but whether the index it tracks can accurately capture the target market and whether its methodology follows industry best practices.
Below, we have compiled from the index providers' official websites the original methodology documents for several well-known indices, including the S&P 500 and the S&P U.S. Indices series, the Nasdaq-100, the Dow Jones Industrial Average, and the Hang Seng Tech Index (full links can be found in the "Reference Links" section at the end). If you are interested in the methodologies of other ETF-tracking indices, feel free to share your thoughts in the comments section:
Index methodology consists of four components:
Construction: Determines which securities are included and which are excluded. Specific criteria may include market capitalization, company headquarters location, trading currency, liquidity, financial metrics such as P/E ratio or dividend yield. The S&P 500's screening process is illustrated in the diagram below. SpaceX's failure to join the S&P 500 was precisely due to failing the fourth layer, the "Profitability Screen"—the hard requirement that both the most recent quarter and the cumulative GAAP net income over the past four consecutive quarters must be positive.
Weighting: Determines the influence of each constituent stock on the index's overall performance. Common methodologies include market-capitalization weighting, float-adjusted market-cap weighting, equal weighting, fundamental weighting, and factor weighting. Indices tracking the same market can produce wildly different constituent lists and trajectories due to different weighting schemes. For example, the S&P 500 uses float-adjusted market-cap weighting, only counting freely tradable shares, meaning companies with larger market caps and more float carry higher weights. The S&P 500 Equal Weight Index, by contrast, assigns an identical weight to all 500 constituents and rebalances periodically. Meanwhile, the oldest index of them all, the Dow Jones Industrial Average, still uses price weighting, where higher-priced stocks carry more weight, regardless of overall company size.
Calculation: Converts constituent data into a specific index point value. The basic logic is: individual stock market cap = share price × shares outstanding; total index market cap = sum of all constituents' market caps; index level = total index market cap ÷ index divisor. The "Divisor" here is a specially designed technical parameter that converts massive market-cap figures into readable index points. It is adjusted accordingly when companies undergo major events such as stock splits, dividends, or spin-offs, ensuring that these corporate actions do not cause artificial jumps in the index level—adjustments typically occur after market close to maintain continuity between the closing value and the next day's opening value.
Rebalance Review: An index is not a static list compiled once and forever; rather, it requires periodic reselection (typically quarterly or annually), removing companies that no longer meet admission criteria, adding higher-ranked new entrants, and updating float share data to accurately reflect actually tradable share counts. Common reasons for a company being deleted from an index include failing to meet eligibility requirements, being replaced by a higher-ranked company, or undergoing corporate events such as mergers, privatization, or delisting. The true decision-maker on this list is the S&P Index Committee—comprised of full-time managing directors from within S&P Dow Jones Indices, with no listed-company executives or external independent members. The committee meets regularly under the publicly disclosed rules framework, but the specific deliberations on individual constituent additions or removals are not disclosed on a case-by-case basis. This is precisely why the market pays such close attention ahead of each rebalancing announcement.
Why Does Everyone Care So Much About Who Gets In?
On May 12, 2025, S&P Dow Jones Indices announced that Coinbase would be officially added to the S&P 500 on May 19, becoming the first cryptocurrency company ever included in the index. Following the announcement, the stock surged 8.8% in after-hours trading. For many entrepreneurs and investors, inclusion in the S&P 500 has come to be seen as a symbolic moment of the industry's formal recognition by the mainstream financial system.
Image credit: Coinbase official X (Twitter) account @coinbase, May 13, 2025; caption: "As the saying goes... First they ignore you, then they laugh at you, then they fight you, then they add you to the S&P 500"
But what generated significant market discussion at the time was that MicroStrategy—which also held massive amounts of Bitcoin and had equally high market recognition—failed to meet the S&P 500 inclusion threshold due to a GAAP net loss of $4.2 billion in Q1 2025. However, when examining the two companies' financial performance more closely, Coinbase's inclusion was not driven by the "hot cryptocurrency narrative" but by actual fundamentals: $65.6 million in Q1 net profit and 24% year-over-year revenue growth. MicroStrategy, no matter how compelling its crypto narrative, remained barred by the profitability threshold in index construction rules as long as its financial statements showed losses.
Does Index Inclusion Equal a Rising Stock Price?
According to index construction methodology, the S&P 500 performs quarterly rebalancing on the third Friday of March, June, September, and December. On the scheduled effective date of index changes, the index rules trigger mechanical buy/sell orders—passive funds tracking the index must buy shares of newly added companies and sell shares of removed ones. The measurable real capital flows can reach billions or even tens of billions of dollars. However, to turn this "whale" of the S&P 500, the rebalancing mechanism is meticulously designed to avoid causing excessive market volatility. Yet every time rebalancing information is released, the resulting market attention and trading sentiment amplify the tendency to chase "inclusion hotspots" for short-term trades, creating the illusion that "inclusion equals guaranteed price gains."
Just two weeks ago (August 14, 2026), S&P Dow Jones Indices announced that Reddit would be officially added to the S&P 500 before market open on August 18. The stock soared as much as 15% in after-hours trading on the news. But the real picture is far more complex. A significant portion of that 15% gain actually came from "short covering"—at the time, approximately 13% of Reddit's float was shorted. When the announcement hit, these short positions were forced to cover, generating a wave of technical buying entirely unrelated to "passive fund inflows." Combined with active fund managers who anticipated the rebalancing and built positions early, by the time passive money actually entered on August 18, much of the price reaction had already been priced in ahead of time.
Beyond short-term effects, however, index inclusion increases a company's long-term capital flows and liquidity. Even more importantly, the social recognition and attention that come with the S&P 500 serve as the most powerful endorsement of a company's overall strength! The New York Fed once analyzed data on companies added to the S&P 500 from 1989 to 2009 and found that companies included in the index had already demonstrated stronger momentum before their inclusion; the post-inclusion gains were, to a large extent, merely a continuation of this "the strong get stronger" momentum, rather than the index inclusion itself creating value out of thin air. This research was later widely cited as the "S&P 500 Index Effect," becoming one of the most widely referenced empirical studies in both academia and the market when examining whether index inclusion truly creates value ex nihilo.
Reference Links
S&P Dow Jones Indices Official Announcement: S&P Dow Jones Indices Consultation on Treatment of MegaCap Companies – Results: https://press.spglobal.com/2026-06-04-S-P-Dow-Jones-Indices-Consultation-on-Treatment-of-MegaCap-Companies-Results
S&P 500 and S&P U.S. Indices Methodology (Chinese version): https://www.spglobal.com/spdji/zh/documents/methodologies/methodology-sp-us-indices-chinese.pdf
S&P 500 and S&P U.S. Indices Methodology (English version): https://www.spglobal.com/spdji/en/documents/methodologies/methodology-sp-us-indices.pdf
Nasdaq-100 Index Methodology (English version): https://indexes.nasdaq.com/docs/Methodology_NDX.pdf
Dow Jones Industrial Average Methodology (English version): https://www.spglobal.com/spdji/en/documents/methodologies/methodology-dj-averages.pdf
Hang Seng Tech Index Methodology (English version): https://www.hsi.com.hk/static/uploads/contents/en/dl_centre/methodologies/IM_hsteche.pdf
S&P Dow Jones Indices Official Announcement: Reddit to be Added to the S&P 500 (August 13, 2026): https://www.spglobal.com/spdji/en/documents/indexnews/announcements/20260813-1484396/1484396_avb54wbs.pdf
Federal Reserve Bank of New York Research Report: The S&P 500 Index Effect (Staff Report No. 484): https://www.newyorkfed.org/research/staff_reports/sr484.html
Disclaimer
This content is provided for informational and educational purposes only and does not constitute investment advice, an investment solicitation, or an offer to purchase or sell any financial product. The indices, ETFs, securities, and market views mentioned herein are intended solely to introduce index construction and passive investing mechanisms and do not represent a recommendation or endorsement by BIT. Historical performance and market reactions to index changes do not guarantee future results. Investing involves risk—securities and ETF prices may fluctuate, and investors may lose part or all of their principal. Please exercise prudent judgment based on your own circumstances. Relevant services and products are subject to the laws, regulations, regulatory requirements, and territorial restrictions of applicable jurisdictions.
