I am saying none of those things. S&P claims their S&P500 index is the "best single gauge of U.S. large-cap equities". That's taken directly from their website.
I dispute this claim, because the (current) rules for S&P500 inclusion exclude companies like SpaceX, Anthropic, and OpenAI. All of these companies are planning to IPO this year, and even if these companies maintain their present valuation for a year, none are eligible for S&P 500. Due to profitability requirements.
Yet these are all U.S. large-cap companies, among the top 20 largest in the U.S., and by S&P's description of the index, should be included. Not including these companies makes the index inaccurate.
> [Google and Microsoft took years go get into the index], so what's new?
Because SpaceX, Anthropic, and OpenAI are $1T+ companies. Google and Microsoft were much smaller relative to the size of the index when they joined.
Best single gauge, not summary. Systematically excluding companies that are large and buzzy yet not profitable is a matter of intentional design to improve the accuracy of the gauge, even if previous companies were not quite this large. Anthropic and OpenAI are great illustrations of why you might want such a design: the bull case for each is that they're going to dunk the other and become the US's primary provider of AI inference, and neither is yet profitable, so by including both of them in the index you're "double counting" investor expectations of how valuable a company producing profitable AI inference will be.