When to Cross the Spread: Curve Following with Singular Control

In this article the problem of curve following in an illiquid market is addressed. Using techniques of singular stochastic control, we extend the results of [NW11] to a twosided limit order market with temporary market impact and resilience, where the bid ask spread is now also controlled. We first show existence and uniqueness of an optimal control. In a second step, a suitable version of the stochastic maximum principle is derived which yields a characterisation of the optimal trading strategy in terms of a nonstandard coupled FBSDE. We show that the optimal control can be characterised via buy, sell and no-trade regions. The new feature is that we now get a nondegenerate no-trade region, which implies that market orders are only used when the spread is small. This allows to describe precisely when it is optimal to cross the bid ask spread, which is a fundamental problem of algorithmic trading. We also show that the controlled system can be described in terms of a reflected BSDE. As an application, we solve the portfolio liquidation problem with passive orders.Stochastic maximum principle, Convex analysis, Fully coupled forward backward stochastic differential equations, Trading in illiquid markets

Liquidity dynamics in an electronic open limit order book: An event study approach

We analyze the dynamics of liquidity in Xetra, an electronic open limit order book. We use the Exchange Liquidity Measure (XLM), a measure of the cost of a roundtrip trade of given size V. This measure captures the price and the quantity dimension of liquidity. We present descriptive statistics, analyze the cross-sectional determinants of the XLM measure and document its intraday pattern. Our main contribution is an analysis of the dynamics of the XLM measure around liquidity shocks. We use intraday event study methodology to analyze how a shock affects the XLM measure. We consider two sets of liquidity shocks, large transactions (which are endogenous events because they originate in the market) and Bloomberg ticker news items (which are exogenous events because they originate outside of the market). We find that resiliency after large transactions is high, i.e., liquidity quickly reverts to normal levels. We further document that large trades take place at times when liquidity is unusually high. We interpret this as evidence that large transactions are timed. The Bloomberg ticker news items do not have a discernible effect on liquidity. --liquidity,limit order book,resiliency

Commonalities in the order book

Recent contributions to microstructure theory hint a commonalities in the price-depth pairs which constitute the open limit order book. In this paper we provide empirical evidence that indeed a small number of latent factors, two for each side of the book, capture most of the variation the price-depth pairs. The results also indicate that a heterogeneous trader population is active on the buy and sell sides. The respective latent factors explaining the by and sell side variation exhibit specific dynamics. When we exploit results from microstructure theory to empirically assess whether the majority of the book variation is due to either informational effects or non-informational fluctuations of liquidity we obtain mixed results.limit order book; commonalities; liquidity; market microstructure

"Risk Reduction in the New Financial Architecture: Realities, Fallacies, and Proposals"

Five times in a decade not yet completed, financial markets have floated to the edge of a whirlpool; in October 1998 they were about to drown when Alan Greenspan threw them a piece of string that, surprisingly, turned out to be a lifeline. The causes for this financial instability lie deep--in the economic theory that urges easy and efficient substitution of one piece of paper for another, always and everywhere; in the technology-driven tight articulation of receipts and payments that Hyman Minsky warned against a generation ago; and in the growth of leverage that diminishes the creditworthiness of major institutions when an interruption in their receipts requires them to seek funds. Meanwhile, as decision-making in finance moves from banks to markets, and the creators of derivative instruments find ways to present uncertainties as risks that can be modeled, time horizons fall and spurious interrelations promote "dynamic hedging" that communicates financial disturbance anywhere to price volatility everywhere. Prevention should be sought in rules to control the creation of leverage in the repo and derivatives markets and in limits on banks' freedom to back away from borrowers' cross-border liabilities in currencies other than their own. Crisis management when prevention fails will require "standstill" agreements to encourage the continuation of something like normal economic life while the losses from merely financial failure are sorted out.

Limit order books and trade informativeness

In the microstructure literature, information asymmetry is an important determinant of market liquidity. The classic setting is that uninformed dedicated liquidity suppliers charge price concessions when incoming market orders are likely to be informationally motivated. In limit order book markets, however, this relationship is less clear, as market participants can switch roles, and freely choose to immediately demand or patiently supply liquidity by submitting either market or limit orders. We study the importance of information asymmetry in limit order books based on a recent sample of thirty German DAX stocks. We find that Hasbrouck’s (1991) measure of trade informativeness Granger-causes book liquidity, in particular that required to fill large market orders. Picking-off risk due to public news induced volatility is more important for top-of-the book liquidity supply. In our multivariate analysis we control for volatility, trading volume, trading intensity and order imbalance to isolate the effect of trade informativeness on book liquidity. JEL Classification: G14 Keywords: Price Impact of Trades , Trading Intensity , Dynamic Duration Models, Spread Decomposition Models , Adverse Selection Ris

How does the Introduction of an ETF Market with Liquidity Providers Impact the Liquidity of the Underlying Stocks?.

This article examines how the inception of an ETF market impacts several dimensions of the liquidity of the ETF-underlying-index stocks. In contrast with previous research, our evidence is based on an ETF market where liquidity providers (LPs) act as market makers. We find that: (1) the market for the underlying stocks becomes more liquid after the ETF ntroduction for investors who trade at the best-limit quotes; (2) but the stock market becomes ess deep for larger traders, most probably because some large liquidity traders exit the underlying stocks’ market for the ETF market. Some statistics suggest that those results could be related to the trading activity of ETF LPs.Transaction Costs; Exchange-Traded Fund (ETF); Index Trading;

"Risk Reduction in the New Financial Architecture: Realities and Fallacies in International Financial Reform"

The causes for the instability that has marked the financial system over past decade lie deep-in the economic theory that urges easy and efficient substitution of one piece of paper for another, in the technology-driven tight articulation of receipts and payments, and in the growth of leverage that diminishes the creditworthiness of major institutions when an interruption in their receipts requires them to seek funds. Many of the proposals aimed at reducing risk in the financial system, however, do not recognize these changes or their importance. The call for greater bank transparency, for example, fails to take into account both that bankers and regulators are jealous of their "privacy" and that financial markets, not banks, have lately become the more important player in the financial system. Guidelines are needed that reflect the new financial architecture: controls on the creation of leverage in the repo and derivatives markets and limits on banks' freedom to back away from borrowers' cross-border liabilities in currencies other than their own. When such preventive measures fail, then crisis management will require "standstill" agreements to encourage the continuation of something like normal economic life while the losses from financial failure are sorted