I was surprised to see Ken Schwaber talking about burn-down charts, as burn-up charts provide more information and are — for me — the preferred option. So this is a short article about burn-up charts and burn-down charts, both great tools for measuring progress.
First, though, a hat-tip to Ian Carroll, a colleague at MEN Media. His blog shows off the video I saw. In it, Ken explains Scrum and answers a few questions from Google employees. It was worth an hour of my time just for his explanation of the wider consequences of dropping quality. The argument may be familiar to you, but the clarity of the explanation and the use of the visual aid (a burn-down chart) is terrific. If you want to see just that then jump to minute 40.
A burn-down chart tracks how much work remains on your project and whether you’ll hit your deadline. The vertical axis measures work remaining. The horizontal axis marks your iterations, and you should mark which iteration is your target end date for the project. After each iteration you mark your progress on the chart and you can project forward to see whether or not you’ll hit your target end date.
In the diagram above we’ve gone four iterations, and the dotted line (the projection) suggests we’ve fallen quite badly behind schedule. After the first iteration you can see we were making good progress, but things changed in the second iteration and alarm bells should have sounded. The project manager should have started doing something then.
A burn-up chart tracks how much work is done. But it shows more information than a burn-down chart because it also has a line showing how much work is in the project as whole (the scope as workload), and this can change. On the burn-down chart it is harder to show a changing goal.
In the diagram the bottom line is the work done and the top line is the total scope. Dotted lines show projections. We can see that the scope remained steady for the first few iterations, and we would have expected to make the deadline. But scope increased around the fifth iteration. Even this wouldn’t have been too bad if that had been the end of it, but it continued to increase after that. The projections show that we won’t make the target deadline at our current rate of scope creep. In fact we probably won’t even make it if the scope remains steady.
More sophisticated burn-up charts can show several scope lines, one for each release milestone. This way the team and the stakeholders can see the effects of, say, moving scope from one release to another.
Burn-down charts have the advantage that they’re simpler — they only show one line. Perhaps that’s why Ken used them in the video; much more would have distracted from his messages. But if you can stand a little complexity then I’d recommend burn-up charts as the more useful option for real-world situations.