The Trillion-Dollar Fight: SpaceX, OpenAI, and the S&P 500 Dilemma

As private tech giants like SpaceX and OpenAI prepare for monumental public listings, a fundamental tension is emerging within the world’s most influential stock index. NYU Stern Professor Aswath Damodaran warns that the struggle to integrate these trillion-dollar entities into the S&P 500 could permanently alter the index's risk profile and the nature of passive investing.

The Battle for Index Inclusion

The recent historic IPO of SpaceX on June 12, 2026, has ignited a debate over how the S&P 500 handles massive, high-growth, yet unproven companies. With OpenAI and Anthropic also lining up for mega-cap listings, S&P Dow Jones Indices faces a paradox: it claims to be a large-cap index, yet it currently excludes some of the largest market-cap players in the world.

To manage this transition, S&P has reaffirmed its rule requiring at least one year of public trading before a company becomes eligible for the index. This means that even if SpaceX, OpenAI, or Anthropic list this year, they likely won't see index inclusion until 2027 at the earliest. Damodaran suggests that while the index needs these companies to maintain its relevance, the companies themselves have little incentive to bend their business models to meet strict index requirements.

Risks to Index Fundamentals

Integrating trillion-dollar companies that are still in their "growth phase" brings significant structural risks. Damodaran points out that even a year after listing, these companies are likely to be money-losing businesses with complex corporate governance structures.

While the S&P 500 uses a divisor adjustment to neutralize the mechanical impact of new additions on the index level, the fundamental composition will shift. Adding these giants would result in:

  • Increased Risk: Higher volatility within the benchmark.
  • Earnings Impact: A near-term hit to the aggregate earnings of the index.
  • Growth Potential: A potential long-term boost to the index's growth profile.

Debunking the "Index Inclusion Windfall" Myth

对于印度和全球投资者来说，一个关键的启示是正在削弱的“指数效应”。许多交易者一直假设，被纳入标普 500 指数（S&P 500）就能保证股价上涨。然而，Damodaran 引用了 1995 年至 2021 年的实证数据，表明纳入指数带来的短期价格跳升已基本消失。

事实上，新加入的公司在进入后的 12 个月内，更有可能表现跑输指数。他以特斯拉（Tesla）在 2020 年 12 月被纳入指数为例，指出该股的表现远逊于其在指数中取代的那家规模较小的房地产投资信托基金（REIT）。对于投资者而言，这意味着基于指数纳入进行交易是一种回报递减的“微利”策略。

核心要点

  • 入选延迟： 由于标普（S&P）的一年交易规则，像 SpaceX 和 OpenAI 这样的万亿美元巨头最早可能要到 2027 年才能进入标普 500 指数。
  • 基本面转变： 将亏损的高增长科技巨头纳入其中，将增加指数的整体风险，并影响其综合盈利状况。
  • 溢价消失： 与纳入指数相关的历史性“价格跳升”正在消退；新入选者在第一年内越来越容易表现跑输基准指数。