In 2009, high frequency trading was estimated to have accounted for
61% of all U.S. equity market volume. That was an all–time high.
But today, it looks like that is no longer the case. In fact, some estimates claim that 2014 will be one of the quietest years for high frequency trading. As a percent of all trading volume, HFT in the U.S. is expected to hit a seven-year low.
That may come as a surprise, considering the release of Michael Lewis' book Flash Boys and the huge increase in mainstream interest around the subject.