I'm responding to only: "> How does the market grow if all trades are zero-sum?"

I'm not trying to say that markets are necessarily a net positive. But we should also not be myopic about it either. There is more to it.

Firstly, money being made solely by trading is rent seeking. It's maybe even the definition of rent seeking (?) Personally I'd be in favor of tax rates in the 40% to 50% region for rent seeking (long term and short term capital gains tax IMO should both be doubled). Perhaps we agree a bit there.

> Money gets created when people take out loans which creates debt which is then traded in the markets

This is still net new money into the market, ergo, the market is not at all zero sum. There is new money flowing into it. That _negates_ the statement that there must be one person losing for every person winning in the stock market, it is not zero sum. Everyone can actually be making money because there is new money being injected (and the opposite can be true when money is net leaving because interest rates are high and everyone is putting their money to cash or bonds instead).

Same thing happens in a Ponzi scheme, everyone can actually be making money while there is new money flowing into the system.

In the example you stated, if a person borrows money against their house, they are moving money away from real estate to the market. Their wealth is net-zero in that scenario, but relative to the market - the market saw a net increase. Thus, the market is not a closed system, it is therefore not by necessity zero-sum - it's possible to have more winners than losers when trading (and/or more losers than winners too)

> If you want to convincingly argue that markets are positive sum you have to demonstrate that markets produce more than they consume in terms of something besides money. E.g. when half of the factory quits to go be day traders, the factory ends up producing more while consuming the same or less.

Yeah, this is what happens with IPO. Oatly is an example, they had a supply crunch, they could not produce enough milk for store shelves. With their IPO money they funded the construction of additional factories to increase their production capacity. I think people forget this, the IPO of a stock is a huge injection of money to a company, as-is whenever the company issues more stock. Amazon is another example, instead of using cash to pay employees, they used stock; which freed up cash to go to other places. Though, post-IPO, shares being traded around is arguably all just rent seeking. A company can still issue more shares too though. This very thing saved both AMC and GME; both of those companies would have gone under if they were not able to raise money by issuing stock.

On the other side, this situation is not always fully pure. Plenty of companies are run by MBAs that give themselves too many shares & their sole goal is to go public so they can offload their holdings rather than grow their company. Still though, the primary reason for stocks to exist is that companies can acquire additional funding without taking out loans, they get that funding by trading ownership. That's still a thing even if there is a lot of other corruption & rent seeking relating to it. Thus, we should not be myopic it, there is more to it.