Work Item States

• Each data series (color band) represents the number of work items that have reached the corresponding state as of the given date. For a more accurate graph, you can use the sums of estimated and actual effort for each of the items, but if your estimates are at consistent granularity, count is easier to compute and just as useful.

Chart Height

• The total height is the total amount of work to be done in the iteration.  If the top line increases, it means that total work is increasing. Typically, the reason is that unplanned work is adding to the total required. That may be expected, if you have scheduled a buffer for unplanned work, such as bug fixing. (See Unplanned Work below.) If the top line decreases, it means that total work is decreasing, probably because work is being cut - either deferred to a future iteration or dropped from scope of the product.

Work in Progress

• Current status is measured by height on a particular date. The remaining backlog is measured by the current height of the leftmost area, Active in this case.  The current completions are shown by the current height of the rightmost area, Closed. The height of the band in-between indicates the work in progress, in this case items Resolved but not Closed.

Resolved

• Watch for variation in the middle bands. An expansion can reveal a bottleneck, for example, if too many items are waiting to be tested and testing resources are inadequate. Alternatively, a significant narrowing of the band could indicate spare capacity.

End Date

• Visually, it is easy to extrapolate an end completion inventory or end date for the backlog from a cumulative flow diagram like this. A small caution applies, however. Many projects observe an S-curve pattern, where progress is steepest in the middle. The common-sense explanations for the slower starting and ending rates are that startup is always a little difficult, and tough problems tend to get handled at the end of a cycle.