“…4 First, HFTs' aggressive orders anticipate short-term price movements and contribute significantly to trading volume. For instance, Brogaard, Hendershott, and Riordan (2014) find that HFTs' aggressive orders predict price changes over very short horizons and account for 25% to 42% of trading volume depending on market capitalization (see also Baron, Brogaard, and Kirilenko (2014), Benos andSagade (2013), andKirilenko et al (2014) for similar evidence). Second, HFTs' aggressive orders are correlated with news such as market-wide returns, quote updates, macroeconomic announcements, E-mini price changes, and newswires items (see Brogaard, Hendershott, and Riordan (2014) and Zhang (2012)).…”