The burn-down chart is also very revealing in regards to the team's estimating success. If the plot is proceeding as expected, and the trend line is an even, steady descent from the top-left corner to the bottom right, this signifies that the team has been extraordinarily successful at predicting its velocity and selecting the right features and right number of features to include in the iterations. If, on the other hand, the line is choppy, sloping up and down and stalling frequently, it can indicate that the team is not cohering efficiently, or that unforeseen complexities are arising that must be addressed. It should be clear that, in all of these circumstances, the PM and the team can use the burn-down chart as a key indicator, not just of progress but of the internal productivity of the team.