My concern is that if everyone is in the passive investing boat then we're no longer following the market, we're making the market, and it's a big departure from the philosophical under-pinnings behind the idea of passive investing.
(We started out letting active players make the market by placing good/bad bets and winning/losing. We got a market that was at least trying to find the right price and we did well due to the low expense ratios. Now that we're in the majority, I'm concerned that no-one is trying to find the right price anymore.)
tldr; I have mixed feelings about passive investing over the long term if we're no longer small fish in a big ocean.
EDIT - I highly recommend watching some of Robert Schiller's Financial Markets lectures on Yale Coursera about general investment theory. Bogle is saying good things, but he simplifies it in a way that I can see might sound disconcertingly incomplete. You're not wrong to ask these questions if you're conscientious and smart enough to want more in-depth answers.
Obviously, these are edge cases (we'll never be 100% passive), but there is some concern that there will be a lock-in effect for companies currently in the S&P... It will be harder to grow if you're not in it, and it'll be harder to fail if you are.
There's also no reason why passive indices have to reflect the total market weighted for market cap.
[0]https://corporate.morningstar.com/US/documents/MethodologyDo...
- http://www.investmentnews.com/article/20170224/FREE/17022994... - https://equityzen.com/blog/alternatives-part-of-investment-p... - http://video.cnbc.com/gallery/?video=3000598150
Disclaimer: Links #2-3 are affiliated with my own company, so you should decided whether or not to believe me.
I'm intrigued by your suspicion ... but I can't put my finger on the exact manner that this might play out ... it's really hazy.
It seems to me that the effect of everyones money going into index funds would be that firms large enough to be in the index would have less and less pressure to issue dividends ... if there is a ready market of buyers of your stock based solely on your size then why bother ?
If money flows, by autopilot, into an asset class wouldn't we expect that asset class to return less and less as time goes on ?
Yes, there are some IPOs, but overall new business starts are still in decline, and large portions of financial markets seem both too systematically risk averse, and yet willing to follow other risks blindly.