A CSR-funded infrastructure improvement project across five schools — new toilet blocks, classroom repairs, and clean drinking-water points — does not need the same evaluation architecture as a national livelihoods intervention reaching half a million people.
Yet impact assessment practice often behaves as though it does: a battery of indicators, data collected across all of them, elaborate sampling, a methodology recommended by funding agencies, and a lengthy report as the default marker of seriousness.
The result is predictable. Smaller, well-bounded projects either skip assessment altogether because it looks unaffordable, or over-invest in methodology that outstrips what the intervention can bear — diverting resources from the work itself.
This is the problem that Principle 4 of the IAAF Impact Assessment Accreditation Standard — Proportionality, Risk and Materiality — is designed to address. Its premise is straightforward: the depth and scope of impact assessment shall be proportionate to the scale, complexity, and risk profile of the intervention, with indicator selection anchored in what is material to stakeholders and decision-making.
The purpose is to prevent both over-engineering and under-analysis. That framing matters because proportionality is sometimes misunderstood as permission to do less.
It is not.
It is a discipline that requires knowing precisely how much assessment is enough — and why.
Proportionality cannot be something adjusted at the reporting stage, once the data has already been collected. It needs to shape the assessment from the beginning.
That means identifying the outcomes that are genuinely material to stakeholders, focusing data collection on what will add value, and allowing the risk profile to determine where deeper analysis is warranted.
A small, low-risk project with limited stakeholder exposure simply carries a different materiality profile than an intervention operating at scale, collaborating with local administration, having multiple funding partners, operating in a sensitive context, or working with vulnerable populations.
The assessment should reflect that difference.
Scoping the work — before a single data point is collected — keeps effort aligned with significance rather than templates or optics.
Right-sizing the assessment does not mean scaling down its rigour. Whatever its size or complexity, a credible assessment needs to make three things visible:
In other words, proportionality itself must be argued — not assumed.
A three-page assessment of a small pilot is credible when it explains why three pages is the right depth for that intervention’s risk and materiality profile. It becomes weak the moment that reasoning is missing — regardless of length.
This is where Principle 4 connects with the rest of the Standard.
Principle 3 — Methodological Rigor and Appropriateness recognises that there is no single “correct” method. A lighter-touch qualitative approach is defensible for a smaller intervention, provided the choice is justified and findings are sufficiently supported rather than asserted from a single thin data source.
Principle 5 — Credible Evidence and Data Integrity sets another important expectation: whatever evidence is gathered, it is traceable, with data gaps and uncertainty disclosed transparently.
And Principle 6 — Contribution and Attribution places a guardrail around claims of contribution or attribution. Those claims need to remain proportionate to the evidence, with alternative explanations acknowledged rather than dismissed.
Read together, these principles make an important point. A lean assessment that is transparent about its scope, honest about its limitations, and modest in its causal claims can be more credible than an elaborate one that overstates what its evidence supports.
The process counts — not the page numbers.
Consider the two examples again.
The five-school infrastructure project has a modest budget, low-risk activities, a limited and easily consulted stakeholder group, and a relatively straightforward risk profile. A short qualitative assessment based on interviews with head teachers, parents, and students may be entirely appropriate — provided its scope is openly justified.
The national livelihoods programme is different. Its scale, financial and reputational stakes, diversity of stakeholders, and potential vulnerability of participants create a more complex assessment environment. It may warrant structured sampling, mixed methods, and stronger contribution analysis.
Neither assessment is inherently more rigorous. Each is rigorous when the approach is appropriate to the intervention and the claims being made.
For any organisation preparing an impact assessment, the proportionality principle offers a useful test before commissioning or designing one. It establishes that credibility is never a function of scale but of appropriateness. The right questions to ask before commissioning any assessment are:
Answering those questions honestly, and documenting the reasoning, allows an assessment to stand on a credible footing.
Proportionality, done properly, is not a way of doing less. It is a way of doing exactly enough — and being able to justify why.
Impact Assessment Accreditation Forum