CRSP's total market indexes, which many of the large total market funds follow. Its interesting to note that his index has historically outperformed the sp500 by like .2% a year too...
The comment you reply to didn't say WeWork is in an index. It's not public yet.
What the comment says: "But there's a big pool of index fund money that will be thrown at this company's stock no matter how poor their governance is or how much self-dealing they do... just because it's public."
