> out unstable, illiquid questionable

So Space X, OpenAI, Anthropic? Those are perfect examples.

It's unlikely their valuations could survive the IPO if their float wasn't extremely low.

> top 20 largest companies in the US market

You do know that S&P weights are based on the free float and not the market cap. So based on that SpaceX etc. will not be in the top 20. The total value of shares of Johnson & Johnson available on the public market will be much higher than that of SpaceX/etc. based on their current valuations.