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Topics: Construction
SPI
I have a conundrum with EVM and I am hoping someone out there can help. Thanks in advance.

Assume a very simple scenario where my project has a BAC or PV of 100 in month 10, accrued at 10 per month, for 10 months. In month 10, my EV is sadly still only 75, for an SPI of 0.75. So I understand from the numbers that we are way behind schedule. So now in month 11, I have no reference PV for that point in time, as my project should have completed in month 10. I cannot continue to use PV = 100, because had I planned 11 months initially the PV surely would have been higher? So I now have an EV of 80, but what is my SPI. It cannot be 0.8 for the reason already stated (i.e. PV cannot still be 100 in month 11), and secondly the SPI metric over time, if I used PV=100, would indicate a performance improvement, which in this very simple scenario, is definitely not true. Any ideas? What do you do after your planned end date?
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Since you are still working in month 11 (and beyond), you factually have a change to the project duration. You should have an approved change request for that, but if nobody cares in your organization you call the shots.

So - arriving at the end of month 10, you should take a prolongation of, say 3 months, draw a new PV curve (recognizing that new PV = old EV for month 1-10) and make an educated guess where on the timeline you will end up and if the PV is reasonable given your old SPI (or you change something with the project setup, e.g. doubling resources).
If you are looking for meaningful EV metrics after the planned completion, you are measuring against a re-plan, not the original plan as Thomas describes. Otherwise PV remains at 100% because that was when you planned to complete all the work.

What I would do for more meaningful metrics at that point is develop a new curve with work remaining only, not total work for the whole project. That will show much better how you are closing the gap starting at zero EV, as opposed to show 80% going to 100%. It is essentially zooming in, to a higher resolution view of where you need to focus without cluttering the data with what you have already completed.
I would agree with Thomas and Keith. I have come across this problem in the past where a planner did not know what to do with the EV after initial planned hours were spent.
The answer was in the change Log. it listed all changes with schedule, effort and cost impacts, signed off from client, (internal / external). With this the estimates could be re-baselined.
In the example above it might give say 120K project costs for 12M duration with an revised EV at the end of Month 10 and a SPI of .83
You did not complete all project works after 10 months, provided that you have got approval for time extension, then you have to re-plan your project with remaining works, approved time, and new BAC (calculated by subtracting AC from EAC). Forget about what you have calculated before, you have to re-calculate PV, EV like you are executing a new project (with remaining works, available time, and remaining budget).
Your SPI will stay under 1, until you re-baseline after an approved CR.
SPI is an indicator that I find not particularly useful, specially towards the end of the project, like in the case you indicated. At the end of the project, SPI equals 1 since all value has been earned. However, this value could have been earned with 10 years delay with respect to the original plan, yet SPI equals 1! It can be a misleading indicator.

As others mentioned, rebaselining is the best course of action to adress the issue, or you may also want to look into another technique, Earned Schedule (https://www.earnedschedule.com/).

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