Highlighting scope change in burndown graphs

I’ve just come across an old Agile Chronicles post about burndown patterns, which makes the following observation:

Flat-line (i.e., zero net progress) – a flat-lined burndown chart may have a number of explanations:

• The team may have been pulled to work on other projects or priorities (i.e., another project, support and maintenance) and has left the current project helpless to succeed.
• The team may be completing work at an expected rate, but new features and/or tasks are being added to the iteration or project as fast as work is being done.
• Defects and rework may be preventing real progress from being made.

We looked a while ago on our project at how to make at least the second of those possibilities explicit on the graph, and came up with a simple solution, which I thought I’d share here. I’m sure it’s not original, but it doesn’t appear to be all that common either, so someone might find it useful.

Basically, if a new user story is added to the scope, or one is removed, this is shown as a vertical discontinuity on the graph at the point where the scope changes. In other words, if you’ve already plotted yesterday’s numbers, you add or remove the new estimate and plot another point for yesterday, rather than just including the scope change with today’s point on the graph.