High-frequency trading is controversial. More than half of all trading now takes place this way, and there's no end in sight to this “arms race” to ever faster speeds. Does it make sense? Is it fair, sensible, or possibly dangerous? New research suggests that HFT does bring benefits as it "synchronizes" the pricing of different related securities, making markets work better for the average investor. Curiously, HFT seems to make assets "flock" together in much the way we see birds flock or fish swim together in schools. Read more at Medium.com.