cheonic730

> A net negative to society, but a positive for the wealthiest.

No.

When your passive index fund manager rebalances every month because “NVDA is now overweighted in VTI, QQQ” the manager does not care about the bid/ask spread.

When VTI is $1.6 trillion, even a $0.01 difference in price translates to a loss $60 million for the passive 401k, IRA, investors.

HFT reduces the bid/ask spread, and “gives this $60 million back” to the passive investors for every $0.01 price difference, every month. Note that VTI mid price at time of writing is $272.49.

> What's the mechanism for removing liquidity?

Liquidity removal = market order

Liquidity providing = limit order (not immediately executable)