[SilasX]

Sure, I was simplifying a bit with the technicals. But you're sure their leeway is enough that they can say "nah, we don't like what the index is doing now, we'll do our own deviations from it?" That seems implausible but I don't know enough about mutual fund/ETF regulations to say for sure.

[nradov]

Yes, I'm sure. You can just read the prospectus itself. Here's one of the biggest ones.

https://investor.vanguard.com/investment-products/mutual-fun...

[SilasX]

I'm aware I can read the prospectus. And, to the extent that I found the relevant portion of the prospectus (that you could have done yourself and posted) here's what I see:

>The Fund employs an indexing investment approach designed to track the performance of the S&P 500 Index (the “Target Index”), a widely recognized benchmark of U.S. stock market performance that is dominated by the stocks of large U.S. companies. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in the stocks that make up the Target Index. The Fund attempts to replicate the Target Index by investing all, or substantially all, of its assets in the stocks that make up the Target Index, holding each stock in approximately the same proportion as its weighting in the Target Index.

That doesn't sound like a lot of leeway to arbitrarily ignore major new additions that make up a few percent of the index. They'd have to say "no, we're not holding each stock anymore".

It would be more informative to see SEC or court rulings on a mutual fund that tried something like this.

Or, we could just go the way HN normally works, and settle it by who can write the most confidently.