A cumulative flow diagram focuses on which curves?

cumulative flow diagram (CFD) is a graphical tool that shows the status of work items for a given period of time. The horizontal axis represents time, and the vertical axis represents the number of work items. The CFD is composed of different colored bands, each representing a different stage of the workflow (such as “to do”, “in progress”, “done”, etc.). The CFD helps visualize the flow of work, identify bottlenecks, and monitor cycle time and throughput1. A cumulative flow diagram focuses on two main curves: the arrival curve and the departure curve. The arrival curve is the top edge of the “to do” band, and it shows the rate at which new work items are added to the system. The departure curve is the top edge of the “done” band, and it shows the rate at which work items are completed and delivered. The difference between the arrival curve and the departure curve represents the amount of work in progress (WIP) in the system2. By comparing the arrival curve and the departure curve, one can assess the stability and predictability of the system. Ideally, the arrival curve and the departure curve should be parallel and close to each other, indicating a smooth and consistent flow of work. If the arrival curve is steeper than the departure curve, it means that more work is entering the system than leaving it, which can lead to increased WIP, longer cycle time, and lower quality. If the departure curve is steeper than the arrival curve, it means that more work is leaving the system than entering it, which can lead to reduced WIP, shorter cycle time, and higher quality3. References: Cumulative Flow Diagram - Scaled Agile Framework, Cumulative Flow Diagrams - Kanbanize, Cumulative Flow Diagram - LeSS