I'm not familiar with these non-intervention clauses, but in the 10/90 scenario haven't you made it much easier to seize control of the company? Now I only need 5%+1 of the shares to do as I wish?
In theory an index fund should never own that much of a company, because that means it would own >50% of all publicly traded companies. The whole point is to spread the risk evenly so you can realize the average returns without having to put any thought into it. It shouldn't mean it's buying $100k shares of GE and also $100k shares of Mom&Pop Pickle Fork Inc.
Naively (ignoring other dynamics of index funds), sure, compared to 100% investors actively engaged in governance. But I suspect investment in index funds replaces largely hands-off direct investment and so, market wide, has virtually no average effect on that (though it may shift the effect among firms compared to those investors doing so directly.)
If that was the case it would have been easy. Handful of people fighting for power.
But from what I can read the problem is exactly the opposite. As someone said below that Blackrock has been known to rubber stamp executive salary and maybe others follow suit. What is then stopping companies from going bigger and bigger on executive salary knowing that they will get rubber stamped from the funds?
What happens if there is a complex governance issue which requires vote and the index fund lack the motivation to ensure that they have weighed all the decisions correctly?
That's a funny contradiction of a sort - then the index fund becomes the agent it's supposed to be observing.
For one, Blackrock is not Berkshire Hathaway - and in reality, obviously Blackrock can't wake up tomorrow and decide to be. They're not built for that.
Another scary thing is that the market is being increasingly turned into a derivative, and the underlying asset becomes more volatile (certainly for many different reasons) as it becomes proportionally smaller .
Is the argument that the vast majority of them could change their funds' charter to allow them to be actively involved with governance? If so, that would be really hard to achieve even if many of them worked at it.
Edit: three people have made the same "it's easier to get a controlling interest" argument. See my reply in the follow-up before making another redundant comment.