I think you and your interlocutors are talking past each other. It's true (and fashionable to point out) that active investment is what makes price discovery, and thus the markets themselves, work. But that doesn't make it a good idea to invest in hedge funds or any other active investment vehicles. Just as Buffett describes earlier in the letter w/r/t the insurance business, active investors can compete the returns on effective price discovery down below the returns on passive investing.
Maybe over the long term the returns on active investing will simply go to prop traders.
Perhaps it is fashionable to point that out where you live, but common wisdom I hear is "everybody should just use index funds", without stopping to ask what would happen if everybody actually did.
Worldwide equities are 65 trillion or so. Can you have a functioning stock market if 1T of that is actively managed by prop traders and the remaining 64T is in passive index funds? I'm not so sure.
Now you're talking past me. It does not follow from the fact that active investment is necessary that people should invest with active investors. Again, fierce competition among active investors can --- and probably have --- created conditions where all the returns on active investing will go to (effectively) proprietary traders.
I don't think I'm talking past you -- your previous point was perfectly clear. You literally cannot have active investments if nobody invests with active investors or actively manages their funds themselves. This is tautological. So somebody has to invest with active investors, but Buffett is arguing it should be somebody else and not you.
If 99.99% of all assets are locked up in buy-and-hold passive index funds the prop traders can't do anything when a stock is mispriced because they can only trade with the handful of active investors that remain. With 65 trillion in equities a handful of prop traders can jump high and low all they want but the markets won't budge if nobody is buying or selling. The index managers on the other hand will be able to move markets with a keystroke, because whenever they decide that one stock in the index has to be replaced by another all the index fund money blindly follows.
You're now litigating the literal definition of a prop trading firm.
Nobody is arguing that you shouldn't start a prop trading firm. The argument is that you shouldn't invest in hedge funds, because passive investment funds outperform them. If you want to make money in active investment, join or form a prop firm.
The broader point would be, the market can probably function based on passive investment and inputs from prop firms, without retail and institutional investors ever needing to engage in active investment. That would also be compatible with the notion that active trading is in general unprofitable because the profit is so aggressively competed out of it.
I literally made this point earlier. I even used the word literally to indicate I meant it literally.
> Nobody is arguing that you shouldn't start a prop trading firm.
I disagree. People are absolutely arguing that nobody should start a prop firm because you can't beat the market. That the prop funds that succeed are just those that have gotten lucky in the short term. That everybody should put their money in index funds instead. I know you don't believe this, but it's a common belief for sure.
I think that if all retail investors and all institutional investors exclusively invest in passive funds the market will get out of whack. We're talking about all pension funds, university endowments, private trusts, all moving to index funds. All households together own about 80% of the stock market (direct + indirect ownership). Hedge funds another 4%. Prop trading firms probably less than 1%. There are over 3500 publicly listed US equities and another 10,000 OTC. Deep analysis on every equity is needed to determine if it is fairly valued; no way prop firms can take on this gargantuan task by themselves.
Not to mention that index funds are long-only. Very few hedge funds are. If almost everybody moved to index funds the long-only bias by itself could be disastrous.
Like I said, I wasn't say you were wrong, I was saying that you and your interlocutors were talking past each other. It can simultaneously be true that active investors can "beat the market" and that retail and institutional investors shouldn't invest in actively-managed funds.
The place I think we got hung up here is on the notion of "nobody investing in", because obviously a person who starts or joins a prop trading firm is in a sense investing in that firm.
It can be true, but my point is that it probably isn't true. And I've explained why I think this. You can look at passive investing as defecting in a large game of prisoner's dilemma (tragedy of the commons). With passive investing you enjoy the benefits of an efficient market without doing any analysis yourself (or paying for somebody else to do it on your behalf). So you can advise every individual to defect (because it's in their best interest) but if too many people defect the system breaks down.
So when you say "It can be true that [...] retail and institutional investors shouldn't invest in actively-managed funds", that can mean two totally opposite things, as hopefully you can now see. That's why we talk past each other. I also suspect there is a real disagreement about what the impact of index funds will be in the long term.
Maybe over the long term the returns on active investing will simply go to prop traders.