This paper directly tests the hypothesis that upstairs intermediation lowers adverse selection cost. We find upstairs market makers effectively screen out information‐motivated orders and execute large liquidity‐motivated orders at a lower cost than the downstairs market. Upstairs markets do not cannibalize or free ride off the downstairs market. In one‐quarter of the trades, the upstairs market offers price improvement over the limit orders available in the consolidated limit order book. Trades are more likely to be executed upstairs at times when liquidity is lower in the downstairs market.

This paper examines the impact of reducing the tick size on market-making behavior on The Toronto Stock Exchange. The results indicate a significant decrease in the percentage of trades of fewer than 10,000 shares involving the upstairs traders and a significant increase in the percentage of trades of fewer than 1,000 share involving the designated market makers. Consistent with this finding, the upstairs traders earn significantly lower returns on non-block trades and the designated market markers earn lower returns on trades smaller than 1,000 shares. We conclude the tick size reduction benefits the trading public.Journal of Economic LiteratureClassification Numbers, G20, G24.

This paper examines the costs and determinants of order aggressiveness. Aggressive orders have larger price impacts but smaller opportunity costs than passive orders. Price impacts are amplified by large orders, small firms, and volatile stock prices. To minimize the implementation shortfall, the optimal strategy is to enter buy (sell) orders at the bid (ask). Aggressive buy (sell) orders tend to follow other aggressive buy (sell) orders and occur when bid–ask spreads are narrow and depth on the same (opposite) side of the limit book is large (small). Aggressive buys are more likely than sells to be motivated by information.