Few people know that the stock market is actually driven more so by cash reserve instruments rather than actual stocks.
The brokers set the price they're willing to buy/sell at. It's really the trade secret. That's where buyers set a limit on their buy/sell waiting for a broker to fulfill it. Everyone is trying to make money, it's just who's willing to fulfill it.
So back to these cash reserve instruments... it could be in the millions or billions. So when they not reinvesting it back as cash reserve, they are probably buying stocks. Not always, as it's the assumption. If they're actually just buying back into the cash reserves or just leaving it as cash, then obviously no stocks are being purchased. That's kind of how it works, but not really either. Cuz them brokers can then inflate the buy/sell by putting up additional order tickets. Which is illegal, but then the SEC has to then conduct an investigation and proove it. Cuz brokers can always claim it was just a duplicated mistake ticket. yeah but hundreds to thousands of duplicated tickets? Exactly when and how many does it count to the point of inflating or deflating the stock value?