Rising End-of-Day Trading in US Equities and Trade Execution Costs

US equity trading activity has become increasingly concentrated near the market close relative to other intraday periods. The share of total trading volume executed in the final 15 minutes of the trading day has increased by more than 40% over the 20 years ending in 2023. Although greater volume can enhance trade matching, financial theory also predicts that thicker markets attract informed traders who can more easily disguise their activity. Consistent with this view, we find that the rise in end-of-day trading has been accompanied by heightened adverse selection and higher trading costs, reshaping key trade-offs faced by market participants.