US Stock Market: SpaceX IPO sparks debate over index inclusion rules and investor risk

SpaceX's public listing has reignited debate over US index inclusion rules, with Nasdaq-100 quickly adding the stock while the S&P 500 has so far refrained, highlighting differing approaches between benchmark providers. The contrast is expected to reinforce Nasdaq's identity as a growth-and-volatility benchmark versus the S&P 500's more conservative methodology, potentially leading to divergent performance as more AI giants like Anthropic and OpenAI prepare to list. The S&P 500 carries greater weight, with its three largest ETFs managing over $3 trillion versus roughly $600 billion for top Nasdaq-100 trackers.