Apportioned effort is work that can't be measured independently, its progress is determined by the progress of another, related work package. The classic example in construction: QA inspection. You can't inspect a steel frame that hasn't been erected. The inspection effort is directly proportional to the fabrication and erection effort. So instead of measuring inspection progress separately, you tie it to the base work package and let that drive the Earned Value.
It's one of three earned value measurement techniques alongside discrete effort (the default, measurable work with defined deliverables) and level of effort (time-based work like project management). Most UK construction teams use discrete effort for everything and wonder why their QA, testing, and commissioning packages produce bizarre CPI numbers. Apportioned effort fixes that.
This term is part of the earned value definitions glossary. For the full earned value formula set, see the formulas page.
The Formula
EV (apportioned) = % complete of base work package x budget of apportioned packageThat's the entire mechanism. The apportioned package doesn't have its own progress measurement. It borrows the percentage complete from whatever discrete work package it's tied to.
If structural steelwork (the base package) is 60% complete and the QA inspection budget is £160,000, then:
EV (QA inspection) = 60% x £160,000 = £96,000
You don't need to measure how much inspection has been done. You don't need to count test certificates. The steel package drives it. Done.
How It Works: Base Package Drives Apportioned EV
The relationship between the base package and the apportioned package is mechanical. The apportioned package has no independent life of its own. It moves in lockstep with the base.
BASE WORK PACKAGE: Structural Steelwork (£2,000,000) APPORTIONED PACKAGE: QA Inspection (£160,000 = 8% of base) Month Base % Complete Base EV Apportioned EV ───── ─────────────── ────────── ────────────── 1 10% £200,000 £16,000 2 25% £500,000 £40,000 3 45% £900,000 £72,000 4 60% £1,200,000 £96,000 5 80% £1,600,000 £128,000 6 100% £2,000,000 £160,000 │ │ │ Apportioned EV = Base % │ │ × Apportioned Budget │ │ │ ▼ ▼ £ BASE PACKAGE APPORTIONED │ ╱╱╱╱╱╱╱╱╱╱╱╱ ╱╱╱╱╱╱╱╱╱╱╱╱ │ ╱╱╱ ╱╱╱ │ ╱╱ ╱╱ │╱╱ ╱╱ ├────────────── Time ├────────────── Time £2.0M at 100% £160K at 100% Same shape. Same trajectory. Different scale.
The apportioned S-curve is a scaled-down copy of the base package S-curve. Always. If the base package accelerates in month 4, so does the apportioned package. If it stalls, both stall.
When to Use Apportioned Effort
Not everything should be apportioned. It's a specific tool for a specific problem. Here's when it works and when it doesn't:
| Work Type | Measurement Technique | Why |
|---|---|---|
| Concrete pours, steelwork, earthworks | Discrete effort | Measurable physical output with defined deliverables |
| QA inspection of structural works | Apportioned effort | Directly proportional to the work being inspected |
| NDT testing of welds | Apportioned effort | Can only test welds that exist; volume tracks welding progress |
| Project management / commercial team | Level of effort | Time-based; no measurable output tied to physical progress |
| Commissioning of M&E systems | Discrete effort | Has its own milestones and deliverables (witness tests, energisation) |
| Health and safety supervision | Level of effort | Ongoing regardless of which base packages are active |
| Material testing (concrete cubes, CBR) | Apportioned effort | Testing volume proportional to placement volume |
The test is straightforward: does this work scale directly with another package's physical progress? Yes? Apportioned. No? Use discrete or LOE.
Worked Example: QA Package on a £20M Water Treatment Project
Worked ExampleScenario: Costain is delivering a £20M NEC4 Option C water treatment works upgrade in Yorkshire. The EVM setup includes a structural concrete package and a QA/testing package.
Base package: Structural concrete, 12 activities, budget £4,800,000, duration months 3 to 14
Apportioned package: QA inspection and testing, budget £384,000 (8% of structural budget)
The 8% ratio comes from the tender build-up. The QA team's costs (two inspectors at £850/day, lab testing at £35K/month) work out to roughly 8% of the structural concrete package.
Month 8 assessment (15 October 2025):
Structural concrete is 55% complete. The site team has poured 2,640 m3 of 4,800 m3 planned.
| Metric | Base (Structural) | Apportioned (QA) |
|---|---|---|
| Budget | £4,800,000 | £384,000 |
| % Complete | 55% | 55% (driven by base) |
| EV | £2,640,000 | £211,200 |
| AC | £2,890,000 | £198,000 |
| CPI | 0.913 | 1.067 |
The structural package is over budget (CPI 0.913, spending £1.10 for every £1 of value). The QA package is under budget (CPI 1.067, the inspectors are being efficient).
Without apportioned effort, the team would need to independently measure QA progress, counting test certificates, tracking inspection hours, estimating percentage complete on a package that doesn't have physical deliverables. That's where arguments start. "Is QA 50% done or 55% done?" With apportioned effort, the answer is automatic: it's whatever the concrete says. 55%.
Combined package view:
Total EV (structural + QA) = £2,640,000 + £211,200 = £2,851,200 Total AC (structural + QA) = £2,890,000 + £198,000 = £3,088,000 Combined CPI = £2,851,200 / £3,088,000 = 0.923
The Ratio Trap
Here's something most textbooks won't tell you. The ratio between the apportioned package and the base package should be set at the start and left alone. Don't adjust it monthly based on "how much QA we think we've done." The entire point is that you don't measure the apportioned package independently.
I've seen teams set a QA package at 8% of structural works, then three months in decide "actually it's more like 12% because we added extra testing." That's a baseline change. If the scope of QA genuinely increased (say, because of a compensation event requiring additional testing), then update the apportioned budget through the proper baseline change process. Don't just fiddle with the ratio.
Apportioned Effort vs Level of Effort
These two get confused constantly. They're fundamentally different.
Apportioned effort is tied to a base package. No base progress, no apportioned EV. It moves with the work.
Level of effort (LOE) is time-based. It earns EV simply by existing for a period. Project management earns EV every month regardless of what's happening on site. LOE always has a CPI of approximately 1.0, which is why too much LOE in your EVM model masks real cost problems.
The danger: if you classify QA inspection as LOE instead of apportioned effort, you earn QA value every month even if the base structural work is stalled. Your overall EV is inflated. Your SPI looks better than reality. And nobody notices until the forecast at completion suddenly jumps by £600K when you're 80% through the job.
Common Mistakes
- Apportioning against the wrong base package. Concrete testing apportioned against steelwork? NDT testing tied to earthworks? Match the apportioned package to the base package it's genuinely proportional to. If the relationship isn't direct, use discrete effort instead.
- Too much apportioned effort in the WBS. If more than 15% of your total budget is apportioned, you've probably classified some discrete work as apportioned out of laziness. Apportioned effort is for genuinely dependent work, not for packages that are "hard to measure."
- Changing the ratio mid-project. Covered above. Set the ratio at baseline, change it only through formal baseline change. Mid-project ratio adjustments corrupt your CPI trend.
- Forgetting to include apportioned AC. You're earning apportioned EV automatically, but are you capturing the actual costs? The QA team's time, the lab testing invoices, the NDT subcontractor, these costs need to land in the apportioned package's AC, not get buried in general prelims.
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Frequently Asked Questions
What percentage of a project budget should be apportioned effort?
On a typical UK infrastructure project, 5% to 12% of the total budget is apportioned effort. QA, testing, inspection, and compliance activities are the usual candidates. If you're above 15%, you've probably misclassified some discrete work. Below 3% and you might be measuring some dependent work independently when you shouldn't be.
Can I apportion against a package that's also partially LOE?
Technically yes, but it creates a measurement problem. If the base package includes level of effort elements, its percentage complete is partly driven by time (not physical progress). The apportioned package then inherits that time-based EV, which defeats the purpose. Best practice: apportion only against packages measured using discrete effort.
What happens if the base package scope changes?
If a compensation event adds scope to the base package (say, additional piling), the base package budget increases and the apportioned package budget should increase proportionally. On the £20M example above, if the structural budget goes from £4.8M to £5.2M, the QA budget should move from £384K to £416K (maintaining the 8% ratio). This is a legitimate baseline change.
Is apportioned effort used on NEC4 contracts?
NEC4 doesn't reference EVM measurement techniques directly. That's a project controls overlay. But apportioned effort works well on NEC4 Option C, where the QA and testing costs are part of Defined Cost and the Accepted Programme provides the baseline for the base work packages. The key is that the apportioned package's costs (AC) map to identifiable Defined Cost items.
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