> If a company is 1-2% of the total US market cap and not included in the index, then the index is wrong right now.

To be clear, S&P 500 relies on float, not total US Market Cap, and Space X will have a tiny float.

Even if it was included, SpaceX would not account for 1-2% of the S&P 500 (more like 0.1%), so even if we reason on the basis of a benchmark, it's not a meaningful difference.