In my work at TAF, I spend a lot of time thinking about impact. Not just whether an investment generates returns, but whether it contributes to meaningful environmental and social change.
The impact investing sector does not suffer from a lack of measurement. Quite the opposite. Investors have never had more scorecards, indicators, dashboards, and reporting frameworks. Yet despite all this activity, a fundamental question often goes unanswered: Are we really measuring our impact?
As scrutiny of ESG and impact claims increases, investors must demonstrate more than the outputs their funding produced. They need credible evidence of the real-world outcomes their investments contributed to—and what they learned when results differed from expectations.
Measuring activity is important. But it isn’t impact.
Output metrics—such as dollars invested, projects supported, equipment installed, or partnerships established—show what was delivered. They help investors manage portfolios, report to boards, and maintain accountability. Outcome metrics answer a different question: what changed because of that activity? Impact goes further still, describing the longer-term systemic change to which those outcomes contribute. All three levels matter, but treating activity as evidence of impact weakens decision-making and credibility.
At TAF, our key outcome metric is annual greenhouse gas emissions reduced or avoided. This is produced [link to calc methodology?] by considering our outputs, for example, the number of building retrofits and the equipment installed or the number of ICE vehicles displaced and charging stations installed. We also consider other desirable co-occurring outcomes related to economic benefits, improved equity, health benefits, and Indigenous reconciliation.
A simple way to distinguish an output from an outcome is the “so what?” test. Planting 1,000 trees is an output. If 50% survive and each sequesters an average of 15 kg of CO₂ per year, the resulting annual reduction of approximately 7,500 kg of CO₂ is an outcome. The example shows why both levels matter: outputs confirm what was delivered, while outcomes show what changed. Impact is the longer-term systemic change that those outcomes help advance.
Climate solutions happen in systems, not silos
Impact investing operates within complex systems. Consider the transition to a low-carbon economy. Emissions reductions rarely result from a single investment, grant, policy, or organization acting alone. Progress typically depends on governments, businesses, utilities, communities, researchers, and capital providers working together over many years. In these situations, proving that a single investor caused an outcome is hard, and proving impact is nearly impossible. A more useful question is:
How did an investment contribute to the outcome, and what evidence supports that conclusion?
This is why contribution is becoming increasingly important in impact measurement—and why TAF is building it into our Impact Monitoring and Assessment approach. Rather than claiming sole credit, we assemble evidence of how our capital helped advance change alongside other actors. Where the evidence supports it, we assess the relative significance of that contribution. This approach is more credible than attribution claims and more useful for learning.
The question we don’t ask often enough
Additionality is arguably one of the most important concepts in impact investing, yet I’ve rarely heard it discussed outside classrooms and theoretical debates. Additionality asks a simple question:
Would this outcome have happened anyway?
For example, one investor finances a climate solution that cannot readily access conventional capital because of technology, market, or execution risks. Another funds a mature climate opportunity with strong demand and abundant financing options. Both investments may generate environmental benefits, but the first likely wouldn’t happen organically and needed the investor, the second did not.
This is why TAF considers whether our capital will reach sectors or opportunities where investment is otherwise scarce – where change is less likely to happen. A recent article in Stanford Social Innovation Review takes the concept even further. The author suggests that when impact investors seek to advance or transform a market, we should not just think about capital scarcity but also ask whether the investment has the ability to change the conditions that made capital difficult to secure in the first place.
Without additionality, impact measurement risks being a record of participation rather than a record of contribution.
Investors measure “potential” better than “actual”
One of impact investing’s most consequential gaps appears between due diligence and evaluation. Before investing, organizations may spend months estimating emissions reductions, forecasting social benefits, and mapping pathways to market transformation. Those projections can shape whether capital is deployed. Yet after an investment matures, exits, or reaches a meaningful milestone, many organizations spend far less time testing whether the assumptions behind those projections proved correct.
- Did the anticipated outcomes materialize?
- Did barriers to adoption actually decline?
- Did the investment mobilize additional capital, influence market behaviour, or accelerate progress that would not otherwise have occurred?
Too often, we know more about the impact we expected to achieve than the outcomes we ultimately did. For a sector built on the premise that capital can drive positive change, this should concern us.
Transitioning from reporting to learning
I believe the next evolution of impact investing is not simply better reporting, but better learning. Recent research suggests that readers use sustainability disclosures as much as financial reporting and may spend longer reading them. Meanwhile, Canada’s voluntary sustainable finance taxonomy is helping investors and other market participants identify and evaluate climate-aligned investment opportunities. In tandem with strong government policies and investments, the taxonomy could become an important tool for investment decisions, lending, transition planning, and climate risk management. These developments matter, but reporting becomes most valuable when investors use it to test assumptions, understand results, and improve future decisions.
Investors should continue tracking operational performance and accountability metrics; those measures remain essential. But reporting should also create a disciplined feedback loop: compare expected outcomes with actual results, test which assumptions held, and examine what the evidence means for future decisions. Doing this well requires transparency about uncertainty and a willingness to treat measurement as a tool for learning—not simply as proof for a report.
This also means using reporting as the start of inquiry, not the end. Test whether expected outcomes occurred, examine how capital contributed alongside other actors, and ask whether the change would have happened anyway. Then use what you learn—including where results fell short—to improve the next investment decision. This is how impact measurement can help direct capital toward the low-carbon, equitable future we are working to build.
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