Let's first address how Earned Schedule improves Earned Value Management's assessment of schedule performance. Then, we will see how AgileESM© adds new insights into the performance of Agile projects.
Earned Value Management measures and tracks time performance using the Schedule Performance Index (SPI). It is a faulty metric. Because of the way it is defined, the SPI rises toward the end of a project, regardless of the actual performance. Even late projects finish with a perfect SPI.
Earned Schedule (ES) solves the problem. Its Schedule Performance Index for time (SPIt) accurately reflects time performance on a project throughout its life span.
The chart below from a recent project, call it Project A, shows the difference. (The SPI is represented by the green circles and the SPIt by the red triangles.) When the project finished late, at Sprint 13, the SPI was a perfect 1.00. The SPIt on the other hand was .80—a more accurate picture of time performance.
AgileESM© adds value to common Agile tools such as burn charts. The Burn Down Chart is a familiar tool used for assessing time performance on Agile projects. It shows how much work has been completed and, by inference, how much remains on the project. Using an end date estimate based on velocity metrics, an Ideal Burn Down line can be added to the previous chart. Results running below the Ideal Burn Down line indicate that the project is behind schedule, and results running above the line imply that it is ahead of schedule.
Let's look at a snapshot of Project A part way through its life cycle (see the chart below). It is clear that, after the re-baseline, the Burndown line shows a steady decline in the number of remaining release points. Through Sprint 8, the results appear to run on or slightly above the Ideal Burn Down line, indicating that the project is on or slightly behind schedule. At Sprint 9, the results jump above the Ideal Burndown line, indicating that the project is definitely behind schedule.
AgileES clarifies what is happening. As shown by the SPIt line (the red triangles), schedule performance efficiency improves over the first four sprints of the new baseline, but after the fourth, Sprint 7, performance steadily declines. While the Burn Down line highlights the deviation at Sprint 9, the shortfall began at Sprint 7. Root cause analysis of the delay should start there, rather than with the later sprint.
In conclusion, there are practical reasons for applying Earned Schedule to Agile projects. As shown by Project A, the SPIt is more accurate than EVM's SPI, and the SPIt offers new insights beyond Agile tools such as burn charts.