Earned value is often blamed when the indices look wrong. The usual fault is not the formula. It is the progress measure changing from week to week. Percent complete one period, remaining duration the next, milestone steps the period after: each may be valid. Mixing them without a rule makes EV jump for reasons that have nothing to do with the site. SPI and CPI then report performance that did not happen.
If you want EVM to tell the truth, fix the measure before you fix the chart.
How inconsistent rules poison EV
EV is the budgeted value of work completed. "Completed" has to mean the same thing on every data date. When it does not, the earn moves because the definition moved.
A package at 40% under a quantity rule can become 70% under a subjective percent the following Friday, with no additional work. Planned value has not changed. Actual cost may not have changed. SPI rises. CPI rises. Leadership congratulates the team. The structure is still late.
Common measures, and why you must pick
| Measure | Works when | Lies when |
|---|---|---|
| Physical % complete | Quantities are measurable and agreed | Someone guesses a feel-good percent |
| Remaining duration | The person who will finish the work sets it | Duration is cut only to hold a milestone date |
| Milestone steps (0/50/100) | Deliverables are clear and binary | Partial work sits at 0 while cost accrues |
| Units complete | Install rates are counted on site | Counts ignore rework or incomplete prerequisites |
| Apportioned effort | True support work tied to a driver | Used to smooth curves on driving scope |
Pick the measure by activity type in the baseline. Write it down. Do not invent a kinder measure in a bad month.
Same rules every data date
The weekly discipline is dull and non-negotiable. The data date moves. Progress is collected against the agreed rule. Remaining duration is reviewed for activities in progress. The file is calculated. Then EV is taken. Not the other way round.
If a rule must change because the work changed, treat it as a controls change: record it, say which activities are affected, and explain the step-change in EV in the narrative. A silent rule change is a silent re-baseline of performance.
Who owns the measure
Ownership has to be named. The planner owns the application of the rule in the schedule. The package manager or site lead owns the factual input. Cost owns the actuals coding that must align with the same WBS. Controls owns the refusal of an update that breaks the rule.
- No EV from a percent the site will not stand behind in writing.
- No remaining duration set by someone who has not walked the work.
- No cost actuals posted to a different structure than the earn.
- No mid-period rule change without a note in the progress log.
When ownership is vague, the kindest number wins. EVM then flatters the meeting.
How SPI and CPI lie after a rule change
Examples are ordinary. A team switches from remaining duration to percent complete on a slow mechanical package. Percents are optimistic. SPI recovers while the commissioning predecessor does not move. Or a team moves to 0/100 milestones to "simplify" reporting. Weeks of cost land against zero earn. CPI collapses. The next week several milestones flip to 100 and CPI spikes. Neither swing was productivity. Both were the rule.
Another pattern: early periods use detailed quantities; later periods use a summary percent because the team is busy. The earn coarsens. Variance against the baseline becomes incomparable. Trend charts still look scientific. They are not.
Weekly discipline that keeps EVM usable
Hold a short progress forum before the data date, not after the pack is drafted. Bring quantities, remaining durations and milestone evidence. Apply the rules. Recalculate. Only then draft SPI, CPI and the narrative. If the indices move, the narrative must say whether the site moved or the measure moved.
Archive the update. Next week, start from that file. Overwriting a single living programme without a saved period destroys the ability to see whether a swing was real.
What directors should refuse
Refuse an SPI recovery that cannot be traced to named activities and an unchanged rule. Refuse a CPI movement explained only as "reporting alignment." Refuse a dashboard that shows indices without stating how percent complete is defined this month.
Ask one question every week: did we measure progress the same way as last data date? If the answer is no, the indices are on probation until the step-change is explained.
The practical standard
EVM is a mirror. It reflects the progress rule you feed it. Feed it a stable rule, and SPI and CPI become useful rates for directors. Feed it a moving definition, and the mirror lies while sounding precise.
EVM Solutions sets progress rules with the baseline and keeps them through the update cycle as part of integrated earned value and controls. If your indices feel theatrical, inspect the measure before you retune the chart. Consistency is not bureaucracy. It is the condition on which the numbers mean anything.
