[wglb]

Keep in mind that many HFTs are market makers and have specific agreements with exchanges that pays them 0.005 cents per share traded, regardless. The other side of this is that they MUST stay in the market, no matter what.

Thus, when trading volume went down over last few years, many HFT firms had less income.

(And to answer another commenter in this thread, No, other investors are not "wise" to the ways of HFT, all traders save for the brokerage firms who used to collect $0.10 on each share traded (the spread before HFT) benefit.)