The figure presents histograms of intraday trading volume distribution, where each bin represents the fraction of total daily customer volume executed per minute (the customer volume during a given minute divided by the total customer volume for the day). The histograms display the average intraday volume fraction per minute for each quarter from 2002Q3 through 2023Q3. The x-axis represents time in minutes from 00:00 to 24:00, while the y-axis indicates the volume fraction (%). Two yellow vertical bars highlight the 15:00 and 16:00 time marks.