[rr888]

> 'HFTs make money by keeping the market liquid'

Ironically they only really keep the market liquid when the sun in shining. When there is a big crash and you really need liquidity most HFTs disappear.

They have put a lot of highly paid human traders out of business though which is something. The C++ devs might be earning a lot but its less than their predecessors.

[slymon99]

Do you have any evidence for this, empirically? I mean yes, HFTs aren't going to let their orders sit stale when FOMC announces a giant rate hike, they aren't going to lose a bunch of money to keep the market healthy. But generally when vol is high, liquidity is at a premium, so I would imagine HFTs become a higher percentage of the market (though spreads are still going to be wider).

[rr888]

Yeah these HFTs aren't big companies, they buy and sell stocks quickly. After the 87 crash big banks could buy billions of dollars of stocks and bonds because banks are huge and could do this to both protect the market, their customers and make money.