We exploit an optional colocation upgrade at NASDAQ OMX Stockholm to assess how speed affects market liquidity. Liquidity improves for the overall market and even for noncolocated trading entities. We find that the upgrade is pursued mainly by participants who engage in market making. Those that upgrade use their enhanced speed to reduce their exposure to adverse selection and to relax their inventory constraints. In particular, the upgraded trading entities remain competitive at the best bid and offer even when their inventories are in their top decile. Our results suggest that increasing the speed of marketmaking participants benefits market liquidity.

We empirically identify a group of stock-exchange accounts that profit from 11 years of earnings surprises. Their trading behavior is consistent with privately informed trading, yet they have negative and temporary price impacts. We then empirically identify a second group of accounts that have positive and permanent price impacts. The trading behavior of the second group is more consistent with trading on public information, and they trade the wrong way before earnings surprises. The behavior of both account groups contrasts with models that associate permanent price impact with privately informed trading.

We examine the role of algorithmic traders (ATs) in liquidity supply and demand in the 30 Deutscher Aktien Index stocks on the Deutsche Boerse in Jan. 2008. ATs represent 52% of market order volume and 64% of nonmarketable limit order volume. ATs more actively monitor market liquidity than human traders. ATs consume liquidity when it is cheap (i.e., when the bid-ask quotes are narrow) and supply liquidity when it is expensive. When spreads are narrow ATs are less likely to submit new orders, less likely to cancel their orders, and more likely to initiate trades. ATs react more quickly to events and even more so when spreads are wide.

Wholesale market makers pay for retail options orders that must be executed on exchanges. Payment for order flow (PFOF) wholesalers compete via price improvement in exchange auctions. To attract retail orders, wholesalers run more auctions when their recent price improvement has been lower. However, auction price improvement lowers market maker revenues. Wholesalers earn revenues to pay PFOF in nonauction trades where their designated market maker status increases their execution priority. While some auctions produce substantial price improvement, most do not have multiple bidders offering meaningful price improvement. Overall, options market structure better promotes competition in auctions than in nonauctions.

We examine the effects of high-frequency traders (HFTs) on liquidity using the September 2008 short sale-ban. To disentangle the separate impacts of short selling by HFTs and non-HFTs, we use an instrumental variables approach exploiting differences in the ban's cross-sectional impact on HFTs and non-HFTs. Non-HFTs’ short selling improves liquidity, as measured by bid-ask spreads. HFTs’ short selling has the opposite effect by adversely selecting limit orders, which can decrease liquidity supplier competition and reduce trading by non-HFTs. The results highlight that some HFTs’ activities are harmful to liquidity during the extremely volatile short-sale ban period.

We examine the role of high-frequency traders (HFTs) in price discovery and price efficiency. Overall HFTs facilitate price efficiency by trading in the direction of permanent price changes and in the opposite direction of transitory pricing errors, both on average and on the highest volatility days. This is done through their liquidity demanding orders. In contrast, HFTs' liquidity supplying orders are adversely selected. The direction of HFTs' trading predicts price changes over short horizons measured in seconds. The direction of HFTs' trading is correlated with public information, such as macro news announcements, market-wide price movements, and limit order book imbalances.

How information is translated into market prices is still an open question. This paper studies the impact of newswire messages on intraday price discovery, liquidity, and trading intensity in an electronic limit order market. We take an objective ex ante measure of the tone of a message to study the impacts of positive, negative, and neutral messages on price discovery and trading activity. As expected, we find higher adverse selection costs around the arrival of newswire messages. Negative messages are associated with higher adverse selection costs than positive or neutral messages. Liquidity increases around positive and neutral messages and decreases around negative messages. Available order book depth as well as the trading intensity increases around all news. Our results suggest that market participants possess different information gathering and processing capabilities and that negative news messages are particularly informative and induce stronger market reactions.

We study quantitative easing (QE) policies from a microstructure perspective, drawing on intraday transaction-level data for German bonds (purchased under the Eurosystem’s QE program). An initial analysis of purchase decisions reveals that portfolio managers consider liquidity and the scarcity of securities in repo markets. Suggestive of significant flow effects, we detect price impacts of purchases at high and low frequencies. We find the impact on market liquidity and functioning to be ambiguous. A higher purchase volume lowers transaction costs but has an adverse impact on order-book depth. The price impact varies with market conditions and is higher for more illiquid bonds.

We test the effects of uncertainty on market liquidity using Hurricane Sandy as a natural experiment. Given the unprecedented strength, scale, and nature of the storm, the potential damages of a landfall near the Greater New York area were unpredictable and therefore uncertain. Using a difference-in-differences setting, we compare the market reactions of Real Estate Investment Trusts (REITs) with and without properties in the widely published evacuation zone of New York City prior to landfall. We find relatively less trading and wider bid-ask spreads in affected REITs. The results confirm theory on the detrimental effects of uncertainty on market functioning.