If a significant percentage of the market is excluded from the index because they don't meet index inclusion criteria, then then index stops being a useful benchmark.

If you change a benchmark whenever you think it'll be 'wrong', then it becomes a measure of the heuristics you use to predict what'll impact the benchmark rather than a benchmark in its own right.

▲

tristanj an hour ago | parent [-]

S&P claims their S&P 500 product is the "best single gauge of U.S. large-cap equities". For this benchmark to be accurate, at a fundamental level, this benchmark has to follow the market and reflect current market conditions.

The market decides what the large-cap U.S. equities are, not S&P. If S&P excludes some of the largest U.S. companies, which based on their current rules, will exclude all of Anthropic, SpaceX, and OpenAI; then they do a poor job reflecting the benchmark they claim to follow.

It's not S&P's fault that market conditions have changed.

▲

onion2k an hour ago | parent [-]

this benchmark has to follow the market and reflect current market conditions

Sure, but right now they don't know how the market will react, so changing the index rules before there's any data would be a measure of their heuristics (e.g. what they believe the market will do), not a measure of what the market is actually doing.

	▲	tristanj 13 minutes ago \| parent [-]
		The core issue is that S&P requires companies to be profitable for 12-months to get included in the index. Yet all of SpaceX, OpenAI, and Anthropic are highly unprofitable, because they are prioritizing investing all free-cash-flow into growth instead of returning money to shareholders. These companies likely will not be profitable for years, and without a rule change it's unlikely they will be included in the index anytime soon. Given these large-cap companies currently represent ~5% of the U.S. stock market capitalization, it's difficult to justify why these companies are excluded from a large-cap index.