We examine quantity choice patterns by equity traders across trading hours in the U.S. Controlling for intraday variations in trading activity, we find that traders submit more non-rounded order sizes and more order sizes overall leading up to a day’s market close. Traders who submit more distinct order sizes pay a higher cost to trade, and they are also less informed about future prices. Our results suggest that the goal to satisfy specific quantity demands rises across the day. This differs from total trading demand, which resembles a U-shape pattern intraday, but is consistent with less trade-size clustering at the ends of fiscal quarters.

We examine U.S. equity trader use of dark and lit markets. Marketable orders executed in the dark have lower information content and smaller fill rates. Dark orders take longer to execute, but they execute at more favorable prices. Traders are more likely to go dark when the bid-ask spread is wider and those with higher dark participation are more sophisticated. Although market regulators have expressed concern over the rise in dark trading, our results indicate that dark markets provide important benefits to traders that lit markets do not.