Concept: Schedule adherence measures how well or poorly the value currently earned matches the value planned to be earned by the ES time. All the value planned and earned as of the ES time is completed in accordance with the scheduled completion of value. Any value earned beyond that is not aligned with the
scheduled completion of value.
Value that is earned out-of-step is generally derived from one of two sources. It either originates from tasks that are impeded or constrained or from tasks that are done prematurely. Let’s first look at tasks that encounter some sort of “road block”.
Practice: It is common for projects to run late. That means tasks often lag behind their planned value. The lags are generally due to impediments or constraints.
An impediment is a problem—a deviation from expectations. For example, a task’s performer falls ill, and the task falls behind.
A constraint is a systemic limitation. For example, a task’s performer fails to complete the required training, and the task fails to finish on time.
In both cases, the result is the same: a negative difference between the amount of value expected as of the ES Time and the value delivered as of the Actual Time.
Figure 1 below depicts such a case. [1]
The curve for Planned Value (PV) represents the cumulative planned value across the timeline and constitutes the Performance Measurement Baseline (PMB). The curve for Earned Value (EV) represents the cumulative earned value. As the EV curve is below the PV curve, the value that has been earned is less than expected—the project is late. [2]
The arrow from the EV curve to the PV curve indicates the time at which the value earned as of the Actual Time should have been earned, i.e., the Earned Schedule (ES). In the example, the ES Time happens to align with the end of Period 3. In reality, that rarely happens, as the ES Time usually falls between period ends.
When a project is running late, the ES Time is earlier than the Actual Time (AT). [3] When a project is running early, the ES Time is later than the Actual Time. In the rare instance that the project is exactly on schedule, the ES Time equals the Actual Time.
Superimposed on the chart is a network diagram. It shows the detailed tasks that make up the project’s PV and EV. Each block on the diagram represents the planned duration of a task. The shaded portion represents the amount of value delivered for the task versus the amount planned for it, i.e., the task’s EV at the Actual Time versus its PV at the ES Time.
The shaded portion of each task on or before the ES Time represents value earned in accordance with the schedule. It counts toward the project’s Schedule Adherence. By contrast, the shaded portions of tasks beyond the ES Time do not count toward Schedule Adherence, as will be discussed in detail in the next post.
Finally, the unshaded portion of Tasks 2, 4, and 6 implies a shortfall in their value as of the ES Time. The shortfall represents a negative difference between their PV@ES and their EV@AT. As just defined, such tasks are impeded or constrained.
Given the frequency with which impediments and constraints occur, it is not surprising that Walt Lipke has declared: “Concentrating management efforts on alleviating the impediments and constraints will have the greatest positive impact on project performance.” (Lipke 2009, p 9. Italics in original.)
Through Schedule Adherence, ES provides a way to pinpoint tasks that warrant investigation for impediments and constraints. It does so by focusing on discrepancies between scheduled value delivery and actual value delivery. Such an approach is well-tuned to making decisions in the presence of scarce resources and uncertainty, especially when other people’s money is at stake. [4]
Notes:
[1] See the Glossary for definitions of the abbreviations in the diagram.
[2] When a project finishes late, the Earned Schedule finishes at the Planned Duration, and the Planned Duration is earlier than the Actual Time.
[3] Knowledge of the deliverables’ value 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. That means their cost must be considered. Glen has several excellent posts on this topic. See Alleman (2017, January 07 and 2018, April 14).
[4] The example is one that appears frequently in Walt Lipke’s publications on Schedule Adherence. See the References section below for details.
Glossary:
AT = Actual Time
BAC = Budget at Completion
ES = Earned Schedule
EV = Earned Value, aka, Budgeted Cost of Work Performed
O/P = Output
PD = Planned Duration
PV = Planned Value, aka, Budgeted Cost of Work Scheduled
$$ = Budgeted Cost
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.
Alleman, G.B. (2018, April 14). Two Parallel Processes of Project Success - Both Value and Delivery are Needed [Blog post]. Retrieved from http://herdingcats.typepad.com/my_weblog/2018/04/two-parallel-process-needed-for-project-success.html. [Reference added14 April 2018.]
Lipke, W. (2013). Schedule Adherence …a useful measure for project management. PM World Journal, Vol II, Issue VI.
Lipke, W. (2012). Schedule Adherence and Rework. CrossTalk, November-December.
Lipke, W. (2011b) Schedule Adherence and Rework. PM World Today, July.
Lipke, W. (2011a) Schedule Adherence and Rework. The Measurable News, Issue 1 (corrected version).
Lipke, W. (2009b). Earned Schedule. Lulu.
Lipke, W. (2009a). 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. |
