Resumen
For base-stock policies, Zhang and Zhang [J. Zhang, J. Zhang, Fill rate of single-stage general periodic review inventory systems, Operations Research Letters 35 (2007) 503–509] derive the fill rate, defined as the long-run average fraction of demand satisfied immediately. We derive the same expression for the fill rate defined as the ratio of expected demand satisfied immediately to expected demand, and generalize to (R,Q) policies.