The final day of each month has become the busiest trading session for US Treasuries, according to two New York Fed researchers. Passive funds have been identified as a key driver of this increased activity, as noted in a Federal Reserve blog. Since 2020, trading activity in benchmark Treasury notes and bonds has been roughly 33 percent higher on the last trading day of the month, on average. Additionally, exchange-traded funds (ETFs) that track Treasuries have grown more than ten-fold between 2013 and mid-2024, although they still represent a small fraction of U.S. Treasuries outstanding. This trend highlights the significance of end-of-month liquidity in the US Treasury market.