Tag Archives: Earned Schedule

The three phases of project controls

The need to control projects (or bodies of work that we would call a project today) extends back thousands of years. Certainly the Ancient Greeks and Romans used contracts and contractors for many public works. This meant the contractors needed to manage the work within a predefined budget and an agreed timeframe.  However, what was done to control projects before the 19th century is unclear – ‘phase 0’.  But from the 1800’s onward there were three distinct phases in the control processes.

Phase 1 – reactive

The concept of using charts to show the intended sequence and timing of the work became firmly established in the 19th century and the modern bar chart was in use by the start of the 20th century. One of the best examples is from a German project in 1910, see: Schürch .  A few years later Henry Gantt started publishing his various charts.


From a controls perspective, these charts were static and reactive. The diagrams enabled management to see, in graphic form, how well work was progressing, and indicated when and where action would be necessary to keep the work on time. However, there is absolutely no documented evidence that any of these charts were ever used as predictive tools to determine schedule outcomes. To estimate the completion of a project, a revised chart had to be drawn based on the current knowledge of the work – a re-estimation process; however, there is no documentation to suggest even this occurred regularly. The focus seemed to be using ‘cheap labour’ to throw resources at the defined problem and get the work back onto program.

Costs management seems to have be little different; the reports of the Royal Commissioners to the English Parliament on the management of the ‘Great Exhibition’ of 1851 clearly show the accurate prediction of cost outcomes. Their 4th report predicted a profit of ₤173,000.  The 5th and final report defined the profit as ₤186,436.18s. 6d. However this forward estimation of cost outcomes does not seem to have transitioned to predicting time outcomes, and there is no real evidence as to how the final profit was ‘estimated’. (See Crystal Palace).

Phase 2 – empirical logic

Karol Adamiecki’s Harmonygraph (1896) introduced two useful concepts to the static views used in bar charts and the various forms of Gantt chart. In a Harmonygraph, the predecessors of each activity are listed at the top and the activities timing and duration are represented by vertical strips of paper pinned to a date scale. As the project changed, the strips could be re-pinned and an updated outcome assessed.

The first step towards a true predictive process to estimate schedule completion based on current performance was the development of PERT and CPM in the late 1950s.  Both used a logic based network to define the relationship between tasks, allowing the effect of the current status at ‘Time Now’ to be cascaded forward and a revised schedule completion calculated.  The problem with CPM and PERT is the remaining work is assumed to occur ‘as planned’ no consideration of actual performance is included in the standard methodology. It was necessary to undertake a complete rescheduling of the project to assess a ‘likely’ outcome.

Cost controls had been using a similar approach for a considerable period. Cost Variances could be included in the spreadsheets and cost reports and their aggregate effect demonstrated, but it was necessary to re-estimate future cost items to predict the likely cost outcome.

Phase 3 – predictive calculations

The first of the true predictive project controls processes was Earned Value (EV). EV was invented in the early 1960s and was formalised in the Cost Schedule Controls System Criteria issued by US DoD in December 1967.  EV uses predetermined performance measures and formula to predict the cost outcome of a project based on performance to date.  Unlike any of the earlier systems a core tenet of EV is to use the current project data to predict a probable cost outcome – the effect of performance efficiencies to date is transposed onto future work. Many and varied assessments of this approach have consistently demonstrated EV is the most reliable of the options for attempting to predict the likely final cost of a project.

Unfortunately EV in its original format was unable to translate its predictions of the final cost outcome (EAC) into time predictions.  On a plotted ‘S-Curve’ it was relatively easy to measure the time difference between when a certain value was planned to be earned and when it was earned (SV time) but the nature of an ‘S-Curve’ meant the current SVt had no relationship to the final time variance.  A similar but different issue made using SPI equally unreliable. The established doctrine was to ‘look to the schedule’ to determine time outcomes. But the schedules were either at ‘Phase 1’ or ‘Phase 2’ capability – not predictive.

A number of options were tried through the 1960s, 70s and 80s to develop a process that could accurately predict schedule completion based on progress to date. ‘Count the Squares’ and ‘Earned Time’ in various guises to name two.  Whilst these systems could provide reasonable information on where the project was at ‘time now’ and overcame some of the limitations in CPM to indicate issues sooner than standard CPM (eg, float burn hiding a lack of productivity), none had a true predictive capability.

The development of Earned Schedule resolved this problem.  Earned Schedule (ES) is a derivative of Earned Value, uses EV data and uses modified EV formula to create a set of ‘time’ information that mirrors EV’s ‘cost’ information to generate a predicted time outcome for the project. Since its release in 2003 studies have consistently shown ES to be as accurate in predicting schedule outcomes as EV is in predicting cost outcomes.  In many respects this is hardly surprising as the underlying data is the same for EV and ES and the ES formula are adaptations of the proven EV formula (see more on Earned Schedule).

Phase 4 – (the future) incorporating uncertainty

The future of the predictive aspects of project controls needs to focus on the underlying uncertainty of all future estimates (including EV and ES).  Monte Carlo and similar techniques need to become a standard addition to the EV and ES processes so the probability of achieving the forecast date can be added into the information used for project decision making. Techniques such as ‘Schedule Density‘ move project controls into the proactive management of uncertainty but again are rarely used.


From the mid 1800s (and probably much earlier) projects and businesses were being managed against ‘plans’.  The plans could be used to identify problems that required management action, but they did not predict the consequential outcome of the progress being achieved.  Assessing a likely outcome required a re-estimation of the remaining work, which was certainly done for the cost outcome on projects such as the construction of the Crystal Palace.

The next stage of development was the use of preceding logic, prototyped by Karol Adamiecki’s Harmonygraph, and made effective by the development of CPM and PERT as dynamic computer algorithms in the late 1950s. However, the default assumption in these ‘tools’ was that all future work would proceed as planned. Re-scheduling was needed to change future activities based on learned experience.

The ability to apply a predictive assessment to determine cost outcomes was introduced through the Earned Value methodology, developed in the early 1960s and standardised in 1967.   However, it was not until 2003 that the limitations in ‘traditional EV’ related to time was finally resolved with the publication of ‘Earned Schedule’.

In the seminal paper defining ES, “Schedule is Different”, the concept of ES was defined as an extension of the graphical technique of schedule conversion (that had long been part of the EVM methodology). ES extended the simple ‘reactive statement’ of the difference between ‘time now’ and the date when PV = EV, by using ‘time’ based formula, derived from EV formula, to predict the expected time outcome for the project.

The Challenge

The question every project controller and project manager needs to take into the New Year is why are more then 90% of project run using 18th century reactive bar charting and the vast majority of the remainder run using 60 year old CPM based approaches, non of which offer any form of predictive assessment.  Don’t they want to know when the project is likely to finish?

It’s certainly important to understand where reactive management is needed to ‘fix problems’, but it is also important to understand the likely project outcome and its consequences so more strategic considerations can be brought into play.

Prediction is difficult (especially about the future) but it is the only way to understand what the likely outcome will be based on current performance, and therefore support value based decision making focused on changing the outcome when necessary.

I have not included dozens or references in this post, all of the papers are available at http://www.mosaicprojects.com.au/PM-History.html

Earned Schedule comes of Age

2013 is the 10th anniversary of the publication in The Measurable News (March & Summer 2003) of Walt Lipke’s seminal paper Schedule is Different, introducing the concept of Earned Schedule (ES) to the world. This milestone was celebrated at the inaugural Governance and Controls Symposium held in Canberra earlier this month.

One of the notable features around ES has been the amount of hostility towards the concept generated by traditional Earned Value advocates (for an overview of ES see: http://www.earnedschedule.com/).

Everyone who understands EV recognises traditional EV is a very useful cost predictor and also recognises that the traditional SPI and SV calculations lose relevance later in the life of a project and fail completely if the project overruns time (ie, in approximately 80% of projects SPI and SV are less then optimal). To resolve this problem, the traditionalists suggest ‘looking to the CPM schedule’ for answers and decry ES.

Unfortunately, whilst a reliable and accurate CPM schedule is a critical underpinning of any competent EV system, CPM itself is a ‘wildly optimistic process’, see: http://www.mosaicprojects.com.au/Resources_Papers_117.html

One step towards eliminating this destructive debate was achieved this month – at last there is definitive research that validates ES as a technique. A research thesis from the AFIT (US Air Force Institute of Technology) Masters student, Capt Kevin Crumrine compares EVM and Earned Schedule indicators on US DoD ACAT 1 programs (for non-military types – ‘big’ programs). The thesis documents a series of five descriptive statistical tests conducted on the Earned Value data for 64 Acquisition Category (ACAT) I MDAP’s. The research found that Earned Schedule was a more timely predictor of schedule overages than Earned Value Management.

Unfortunately the statistical data did not compare ES with the CPM predictions. The thesis notes ‘One shortcoming to this research is the inability to map the Earned Schedule data to the critical path, but we consider Earned Schedule to be a strong tool for schedule prediction at the summary/contract level.’ The stated reason was ‘Our example produced earned value data no deeper than the Work Breakdown Schedule (WBS) level 3 (ex: WBS Element 1.2.3). The Critical Path data is collected much deeper, as detailed as WBS level 7 (ex: WBS Element This disconnect prevented us from conducting a detailed analysis’

My feeling is the detailed nature of Capt Crumrine’s analysis meant the researcher could not see the ‘wood for the trees’. The only date that really matters on most projects/programs is the completion date! The level the data is collected at does not matter; neither does the activity/work package that that actually drives the final completion. What matters is the end date!!! The fact ES is a better predictor then EV should be 100% accepted and proved by now, and if not this detailed thesis should remove any residual doubts.

What is not proved is does ES provide a more reliable end date than CPM? My assessment outlined in Why Critical Path Scheduling (CPM) is Wildly Optimistic is that ES should be more accurate. Given the mass of data collected by Capt Crumrine it would be a pity if this last step is not applied by a future researcher.

The key role of CPM is (or should be) making the best use of the currently available resources on a project – this is the antitheses of predicting outcomes based on current trends in the way ES does. All that’s needed is another Masters candidate!!

Capt Kevin Crumrine’s thesis, ‘A Comparison of Earned Value Management and Earned Schedule as Schedule Predictors on DoD ACAT I Programs’ is now in the CPM electronic library at http://www.evmlibrary.org/library/Crumrine%20Final%20Thesis.pdf. If you are into analysis it is well worth the read.

Sydney workshops

There are a series of workshops planned for Sydney over the next few weeks we highly recommend:

Workshop 1: Applying Earned Value to Commercial [IT] Projects
This course has been crafted to allow project managers to decide for themselves whether they want to improve the performance of their projects by apply the principles of Earned Value without the overhead associated with large, complex Department of Defence acquisition contracts.

Workshop 2: Earned Schedule Masterclass
Earned schedule analysis is a breakthrough analytical technique that derives schedule performance measures in units of time, rather than cost. The same basic EVM data points are used. Indicators, similar to those for cost, are derivable from the earned schedule measure. These indicators provide a status and predictive ability for schedule, analogous to cost.

Workshop 3: Approaches to and Lessons Learned from “Internal Project Surveillance” with Lisa Wolf EVP, PMP. Lisa is the Earned Value Management (EVM) Focal Point for Booz Allen Hamilton, a leading USA global consulting firm that is committed to delivering results that endure.

This workshop focuses on the approaches which can be adopted and lessons learned in setting up an internal project management surveillance function which comes from Booz Allen Hamilton’s internal experience as well as extensive experience assisting US Government agencies and other clients. Best practices which are essential for successfully establishing this function including processes, procedures, and vital internal relationship-building will be explored.

For more information on these workshops see: ‘Upcoming Events’ at http://pmisydney.org/

Earned Schedule

In the March 2003 edition of the PMI College of Performance Management journal, The Measurable News Walt Lipke published his seminal paper “Schedule Is Different” and introduced the world to Earned Schedule (ES).

The challenge of predicting the likely completion date for a project is fraught with issues. There are no established protocols for scaling the remaining durations in a CPM schedule to take account of actual performance to date and there is no way of dealing with the consequences of a ‘bow wave’ of non-critical tasks consuming float until after they hit the critical path.

Re-scheduling the project is the same as re-estimating the work, a practice long discredited by Earned Value (EV) professional as being less accurate and more expensive than using EV formula to calculate a predicted cost outcome. And, the SPI and SV calculations cease to have any validity as the original project completion date is approached. In short, SPI does not work and CPM is wildly optimistic.

Earned Schedule

Earned Schedule

Walt solved this problem at least in part with the invention of ES. ES uses standard EV data to calculate a set of schedule indicators, which behave correctly over the entire period of project performance. The methodology and spreadsheets needed for calculation are freely available from the ES website.

Now Walt has published a sensibly priced book that explains the concept of ES and additional advances to the theory and practice of ES including the “P” factor, a measure of schedule adherence and “Effective EV,” which discounts the EV accrued by EV earned out of the correct process sequence.

I downloaded a PDF version of Walt’s book from Lulu Publishing for under $15; printed paperback books are available from Amazon, Lulu and a range of other book sellers.

Used properly, ES is the bridge between EVM cost and network schedule analysis, improving and providing the base for further developments in cost-schedule integration. ES can’t replace scheduling (and does not seek to) but it does provide a useful insight above and beyond what’s achievable using either traditional EV calculations or traditional CPM scheduling.

This is a book serious project control professionals cannot afford to ignore!

Earned Schedule

Earned Schedule (ES) is emerging as a valuable tool in the overall management of projects. In our view, the ES methodology provides a valuable adjunct to, and a useful sanity check of, the ‘critical path’ (CPM) schedule developed for a project, for very little effort – provided the project has implemented Earned Value Management (EVM).

Using the same data as EVM, ES ‘scales’ the remaining duration of the project based on the volume of work accomplished to date compared to the planned volume, as measured by SPI(t).  SPI(t) has the potential to predict future slippages that the CPM schedule may not be indicating.

CPM schedules have two major flaws inherent in the methodology:

a.  CPM assumes all future work will be accomplished as planned. There is no ‘scaling function’ for the performance of future work similar to the EVM calculations of EAC = BAC/CPI for cost.

b. CPM schedules do not show critical path slippage if ‘float’ is being consumed. The ‘bow wave’ of delayed work eventually becomes critical (usually with disastrous consequences) but there may not be pre-warning.  (for more on scheduling see: http://www.mosaicprojects.com.au/Planning.html)

Research by Henderson and Zwikael has demonstrated that CPI and SPI(t) are closely correlated at a summary level across a range of commercial projects. This and other research suggests ES will provide a valuable management insight to help the successful delivery of projects, but whilst this debate needs to be finalised it will ultimately be determined in the marketplace.

The Earned Schedule tools are freely available from http://www.earnedschedule.com together with published papers and links to other sites.