Do Dark Pools Harm Price Discovery?∗ Haoxiang Zhu Graduate School of Business, Stanford University October 23, 2011 Abstract Dark pools are equity trading systems that do not display orders publicly. Orders in dark pools are matched within the exchange bid-ask spread, without a guarantee of execution. Informed traders tend to cluster on one side of the market and therefore, when submitting orders to a dark pool, face a lower execution probability than uninformed traders, whose orders are relatively uncorrelated. Consequently, dark pools are more attractive to liquidity traders, whereas exchanges are more attractive to informed traders. Adding a dark pool tends to concentrate payoff-relevant information onto the exchange and, under natural conditions, improves price discovery. Keywords: dark pools, price discovery, liquidity, fragmentation, equity market structure JEL Classifications: G12, G14, G18 ∗First version: November 2010. I am very grateful to Darrell Duffie, Sal Arnuk, Jonathan Berk, John Beshears, Bradyn Breon-Drish, Peter DeMarzo, Thomas George, Steven Grenadier, Frank Hatheway, Dirk Jenter, Ron Kaniel, Arthur Korteweg, Ilan Kremer, Charles Lee, Han Lee, Ian Martin, Jim McLoughlin, Albert Menkveld, Stefan Nagel, Francisco P´erez-Gonz´alez,Paul Pfleiderer, Monika Piazzesi, Martin Schneider, Ken Singleton, Jeffrey Smith, Ilya Strebulaev, Mao Ye, Ruiling Zeng, Jeff Zwiebel, and seminar participants at Stanford University, the joint Stanford- Berkeley student seminar, and the Western Finance Association meeting for helpful comments. All errors are my own. Corresponding address: Stanford Graduate School of Business, 655 Knight Way, Stanford, CA 94305-7298. Email:
[email protected]. Paper URL: http://ssrn.com/abstract=1712173 1 1 Introduction Dark pools are equity trading systems that do not display orders publicly.