As I've mentioned elsewhere in the thread, it's notoriously difficult to get citations on this stuff so take with a grain of salt, but I've heard that in 2019 the "HFT" industry (defined some way) had cumulative annual profits in the US of somewhere between 2-4 billion dollars. That's a long holiday weekend for Google or FB. I've also heard that this (inflation-adjusted etc. etc.) this is down sharply from ten years before, when spreads were wide and undocumented order types were winked at.

To wildly oversimplify, market makers will tend to drive the spread down to the tick size, and arbitrageurs will tend to put themselves out of a job.

For the industry as a whole to be growing either in distinct actors or cumulative top-line, the number of markets and instruments and general financial activity has to be growing faster than the big dogs are eating each other. This is my (semi-informed) guess.

> HFT industry annual profits 2-4 billion. That's a long holiday weekend for Google or FB

Nitpick: that’s 10 to 37 days for Google or FB. 2B for Google is ~10 days, 4B for Meta is 37 days. Alphabet net income for 2021 was $76.033B, Meta Net income $39.370B.

Haha fair play, but to nitpick in return: when I worked on FB Ads, revenue was not even remotely uniformly distributed across days of the year, and Thanksgiving? Lots of family photos going up and being looked at relative to your typical Thursday.

Morbidly funny anecdote: when I first moved to the NYC office I obviously didn't have many friends, let alone a significant other. Myself and a few of the other sad saps who failed to notice the office clearing out a bit early around us were borderline freaking out over what looked like very anomalous behavior in the IG ranking system.

It wasn't until we raised it in a slack group that included some coupled folks that we realized it was Valentines day. Womp Womp. ;)