Concept: Schedule adherence measures how well or poorly the planned sequence of deliverables is being followed. That is not a measure of % Complete. Nor is it even a measure of Physical % Complete. It is a measure of the value earned versus the value planned to be earned by the ES time.
Practice: A common view is that project performance is measured by % Complete. [1] In this view, Schedule Adherence is the current % Complete over the planned % Complete. Such a view has a severe limitation.
The % Complete is often calculated as the spent duration versus the planned duration. [2] Progress is measured by the consumption of time. But, what is delivered for that amount of time? In the absence of tangible results, the metric only measures ticks of the clock.
Physical Percent Complete (P%C) shifts the focus away from duration to deliverables, specifically the number of deliverables completed versus the number planned to be complete. The deliverables are tangible results such as the number of bricks laid in a wall or the number of architectural drawings produced for a building.
P%C rightly focuses on deliverables and is our preferred metric for % Complete. But, there is still something missing: the cost to complete the deliverables. Knowledge of the deliverables’ cost is crucial to making project decisions. Why? Because those decisions are tied up with how (other people’s) money is being spent. The decisions operate in the world of scarce resources and uncertainty. As Glen Alleman points out, such decisions are bound by the principles of Microeconomics, and that means we need to know the deliverables’ cost and, beyond that, the value being produced (Alleman 2017, January 17).
In EVM, value is a function of deliverable counts and costs: the deliverables produced multiplied by the planned cost to produce them. [3] That yields the Planned Value (PV), aka, the Budgeted Cost of Work Scheduled (BCWS). As deliverables are completed, value is earned (EV). The Earned Value is also known as the Budgeted Cost of Work Performed (BCWP). By mapping PV and EV into units of time, ES extends the picture beyond costs to the “time value” of the deliverables.
As explained in detail elsewhere, Earned Schedule is the time at which the value currently earned should have been earned. [4] If execution strictly follows the plan, the value delivered exactly follows the planned sequence of value delivery. The ES time and Actual Time are the same. Figure 1 depicts such a case. [5]
Figure 1
From Figure 1, it is clear that all the value earned thus far has been earned as of the ES time. Any deviation from that pattern of earned value is a deviation from the schedule, i.e., the scheduled delivery of value.
This has implications for a case like that depicted in Figure 2, where the project is late. [6]
Figure 2
In this case, there is a gap between the ES time and the Actual Time. The principle, however, still applies: all the value planned and earned as of the ES time is completed in accordance with the scheduled completion of value. Any value earned outside that, as in Tasks 5, 7, and 8, is not aligned with the scheduled completion of value. In short, they are out of step with the schedule.
In the next post, I will describe the implications of being in step or out of step with the scheduled delivery of value.
Notes
[1] See the following PMI article as an instance: Salapatas, J. N. (1985). Performance measurement for projects and project management. Project Management Journal, 16(3), 29–33. https://www.pmi.org/learning/library/performance-measurement-projects-management-5259.
[2] For example, in MS Project % Complete is calculated as Actual Duration / Planned Duration.
[3] Why “planned cost” rather than “actual cost”? As Glen Alleman says, “The actual cost to do the work is a cost management issue, not a schedule management issue.” See http://herdingcats.typepad.com/my_weblog/2009/01/earned-value-an.html.
[4] See Lipke (2009), p 8, the comment superimposed on Figure 1. For an earlier mention of this way to express ES, see Lipke (2006). See also my 19 April 2015 blog post on this topic http://www.projectflightdeck.com/cESExchange000.php?blog_archive=2015-04.
[5] Figure 1 is found throughout Walt’s articles on Schedule Adherence, e.g., Lipke 2009a, p 8.
[6] Again, the figure is cited frequently by Walt, e.g., Lipke 2009a, p 9.
References
Alleman, G.B. (2017, January 07). Economics of Software Development [Blog post]. Retrieved from http://herdingcats.typepad.com/my_weblog/2017/01/economics-of-software-development.html.
Lipke, W. (2011). Schedule Adherence and Rework. The Measurable News, Issue 1 (corrected version).
Lipke, W. (2009). Schedule Adherence …a useful measure for project management. The Measurable News, Issue 3.
Lipke, W. (2008). Schedule Adherence: A Useful Measure for Project Management,” CrossTalk, April.
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