[tshaddox]

That ignores the actual issue here, which is the change in rules. Index funds already seek to own the entire market, and when most people chose these index funds there were rules about when newly listed stocks get purchased by the funds. And now those rules are being changed.

[bluGill]

Index funds generally try to match the performance of the index, but most are not required to hold the same companies as the index itself does. They typically do, but managers often have choices.

[eru]

> Index funds already seek to own the entire market, [...]

No, it depends on the index in question.

[tshaddox]

Yes, most index funds don't literally intend to own the entire market for any sufficiently broad interpretation of the word "entire."

But the point is that we have notable index funds which are marketed to customers as having the intention to own segments of the market according to certain rules, and they are changing those rules with relatively short notice and for reasons that seem suspicious to many customers.

[eru]

> Yes, most index funds don't literally intend to own the entire market for any sufficiently broad interpretation of the word "entire."

I mean that your index doesn't even have to own a segment of the market. Just look at eg how the Dow Jones Industrial Average is constructed. When a company has a stock split, it changes its weight in that index. That has nothing to do with 'the market'. (Stock splits have approximately no influence on your weight in the S&P500.)

Or you could have an index that captures all the stocks whose ticker starts with X minus those that start with Y plus the current temperature in Frankfort, Kentucky, in Rankine degrees.