There is a huge amount of misinformation on this topic, including in this thread, at the minute.

Some index funds have a very long horizon before they include them (e.g. a year). Others are "fast-tracked" (e.g. notably VTI). Most of those, however, are float-adjusted, so only the stock available for trade is considered part of the marketcap. So e.g. VTI / VTSAX will buy spacex relatively quickly after the IPO but at the float-adjusted weight of ~$75B because that's the % of stock available.

If you care alot about this, now is the time to understand how your index fund treats IPOs wrt to delays + float adjustment.

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avensec an hour ago | parent [-]

Do you have any suggested reading references?

Specifically, I do a typical 3FP and own VTSAX, but I don't read bogleheads or anything. True set-it-and-forget-it, but I do want to read more if things are shifting.

	▲	lbrandy an hour ago \| parent [-]
		You should not trust me, but here's my understanding. I wish there was a really good writeup somewhere to explain this authoritatively but I'm not sure there is one. Would also love to see one. Frankly vanguard should do it. VTSAX (and VTI) follow the CRSP index. This is float-adjusted but they likely will be fast tracked (these are two separate rules in how this index chooses to weight things and participate in new stocks). At ~5% float, these companies will be in the 50-100B range. So under all those assumptions, they'll be bought quickly but represent less than 1% of VTSAX (until they float more shares on the public market).