[ben_w]

I've recently learned a new finance term, "float", and I want to check if this makes a difference to this discussion?

https://en.wikipedia.org/wiki/Public_float

I hear S&P 500 is weighted on float rather than on market cap, while Nasdaq 100 is based on market cap.

[eru]

Yes, that's mostly correct. Many indices are weighted by something like free float.

[outside1234]

Yes, and in this case, it means that SpaceX will only be approximately 0.1% of the SP500.

[HWR_14]

NASDAQ will be weighted by 3xfloat upto 100% when SpaceX goes public.

[petesergeant]

One of the places you could have learned this would be the article itself:

> most share indices weight firms in proportion to the value only of shares they have released for public trading (the “free float”). For SpaceX, this means just the $75bn or so of stock it intends to issue in June—so its initial weight in the S&P 500 will be around 0.1%. The NASDAQ 100 is an exception, and has changed its rules to weight companies at up to three times their free float, in an apparent effort to woo Mr Musk. Even so, SpaceX’s probable initial weight in this $40trn index will still only be around 0.5%.