Overlapping trading hours concentrate activity and create a temporal window in which liquidity can be supplied, consumed, and transferred across venues. Liquidity provision during these overlaps tends to be deeper and more continuous because market makers and algorithmic traders can hedge and arbitrage across correlated books in real time. Research by Terrence Hendershott University of California Berkeley, Charles M. Jones Columbia Business School, and Albert J. Menkveld VU University Amsterdam attributes part of the post-2000 improvement in quoted spreads to faster intervenue trading and algorithmic strategies that operate precisely in overlapping sessions. At the same time, Joel Hasbrouck New York University documents how price discovery becomes distributed across venues when trading hours coincide, so information incorporated on one exchange rapidly affects quotes elsewhere.
Liquidity dynamics during overlap
When markets overlap, order flow correlations rise and liquidity providers can net exposures across books, lowering marginal costs of quoting. Algorithmic trading and high-frequency market making benefit because they can monitor order books simultaneously and provide two-sided quotes while managing short holding periods. Models by Ricardo Avellaneda Courant Institute of Mathematical Sciences and Sasha Stoikov illustrate how market makers adjust quotes when they can dynamically hedge in related venues, making liquidity provision more resilient during normal conditions. However, overlaps also create channels for rapid information transmission: a shock in one venue can trigger synchronized withdrawal of quotes elsewhere, amplifying temporary illiquidity.
Risks and structural consequences
Overlapping hours reinforce cross-market linkages that have regulatory, cultural, and territorial implications. Exchanges in different time zones negotiate access, order-routing arrangements, and disclosure rules that affect who can supply liquidity and when. In emerging markets, local participants may depend on liquidity that flows from larger venues during overlap, making them vulnerable if global providers withdraw. Conversely, overlapping sessions can support broader market access for global investors, enhancing capital allocation across regions. Empirical work on intermarket microstructure emphasizes that while overlaps generally reduce transaction costs and improve efficiency, they also raise systemic sensitivity to rapid, cross-border flows and to heterogeneous rules governing market access and best execution.
Understanding these trade-offs requires combining microstructure models with empirical analysis of order books and regulatory contexts. Policymakers and exchanges must balance the efficiency gains from temporal overlap with safeguards that limit contagion and ensure fair access for diverse participants.