Why cumulative and lag-one forecasts matter for inventory decisions

Nicolas Vandeput argues that cumulative accuracy across the replenishment risk horizon is often more relevant to inventory decisions than isolated period accuracy. He also explains why lag-one performance remains important even when immediate orders are already fixed.

Forecast KPIs must match the decision being supported. Inventory owners should define lead time, review period, lost-sales or backorder behavior and the aggregation level before selecting metrics. Dashboards that report only one lag can hide systematic errors affecting inventory planning.