“…Indeed, on the one hand, some studies have highlighted the benefits of HFT as a source of an almost continuous flow of liquidity (see e.g., Brogaard, 2010;Menkveld, 2013). On the other hand, other works (see e.g., SEC, 2010;Angel, Harris, and Spatt, 2011;Lin, 2012;Kirilenko and Lo, 2013) have pointed to HFT as a source of higher volatility in markets and as a key driver in the generation of extreme events like flash crashes, whose incidence has grown in the last decades (Johnson, Zhao, Hunsader, Meng, Ravindar, Carran, and Tivnan, 2012;Golub, Keane, and Poon, 2012). The regulatory framework is complicated by the fact that -although many explanations have so far been proposed for flash crashes -no consensus has yet emerged about the fundamental causes of these extreme phenomena (see Haldane, 2011).…”