The US Federal Reserve Board published research assessing how US Treasury market liquidity could deteriorate under adverse shocks, rather than focusing only on current trading costs. The paper finds that reduced market depth, defined as the availability of resting orders to trade, is associated with greater liquidity fragility. The analysis attributes this relationship to lower depth making low trading costs more dependent on the rapid replenishment of resting orders. The results hold across the major benchmark Treasury securities when analysed individually, supporting analogous conclusions about market-wide liquidity fragility.