Résumé en anglais

This article provides new insights into market competition between traditional exchanges and alternative trading systems in Europe. It investigates the relationship between the trading activity of a crossing network (CN) and the liquidity of a traditional dealer market (DM) by comparing data from the SEAQ quote-driven segment of the London Stock Exchange (LSE) and internal data from the POSIT crossing network. A cross-sectional analysis of bid-ask spreads shows that DM spreads are negatively related to CN executions. Risk-sharing benefits from CN trading dominate fragmentation and cream-skimming costs. Further, risk-sharing gains are found to be related to dealer trading in the CN.