The answer is simple: fundamentals are not driving stock prices -- instead it's money flows that matter. And 90% of those money flows are coming from computer-based trading algorithms, not investors trading on fundamentals. All those [relatively new assets such as passive index or exchange-traded funds such as the Total Stock Market ETF which holds $102 billion 19% more than a year ago] are untested over any duration of time with severe stress. Indeed high frequency trading -- which peaked a decade ago -- remains a large, though much less lucrative driver of market activity than it once was. The key to success in high frequency trading is the speed at which computers -- located near the exchanges computers -- can operate.

Source: Forbes October 22, 2018 14:48 UTC