A common graph used together with Kanban is the cumulative flow diagram. It looks like what is shown in the following diagram:
A cumulative flow diagram shows the number of items in each column
The diagram shows the accumulated number of issues in a flow with the four statuses: Todo, In dev, Test, and Done. After one day there are 3 issues on the board, 2 in Todo, and 1 in In dev. On day 9 there is 1 issue Done. That means we have spent 8 days to complete it, which means that is we have a lead-time of 8 days. At the same day there are 13 not done things on the board. The Todo line is on 14 and 1 thing is in Done. This means you can see lead-time as the horizontal difference between the Todo line and the Done line and the WiP as the vertical difference between the same lines. You can see the actual amount a certain date and the trend. If the difference between two lines is increasing you can expect there is a bottleneck in your system.
The advantage of the cumulative...