Measuring Impact: Why and How?

Does the growth of an impact-driven company automatically lead to an increase in its impact? Not necessarily. Rebound effects, negative externalities, blind spots: without structured measurement, impact remains an intention, not a reality that can be managed. In this article, we explore why and how to measure your impact in a meaningful and credible way.

In this article, you will learn:

• Why economic growth does not guarantee an increase in impact
• What rebound effects are and why they can be misleading (examples: second-hand goods, repackaging)
• How to build a theory of change to structure your measurement
• Which indicators to choose—and which to avoid
• How Deuxième Avis uses impact measurement as a strategic management tool
• How to integrate measurement into governance in a sustainable way

Why measure impact?

Impact cannot be automatically inferred from growth

A widely held belief is that the growth of an impact company’s impact naturally follows its economic growth trajectory.

In reality, this relationship is by no means automatic. Growth increases volumes, but also the complexity of the effects generated: indirect effects, negative externalities, rebound effects, or impact displacement.

Without measurement, it becomes very difficult to know whether impact is actually improving, stagnating… or deteriorating.

Understanding rebound effects and third-party effects

Impact measurement specifically helps shed light on these effects that are invisible at first glance.

A frequently cited example is the second-hand market. Intuitively, buying a used product always seems more virtuous than buying new. However, several studies have shown that the massive growth of the second-hand market can generate a rebound effect:

• a decrease in perceived cost,
• increased overall consumption,
• a smaller-than-expected reduction in new production.

Platforms like Vinted have thus been questioned about their actual impact: without detailed measurement, it is difficult to know whether they are effectively replacing new purchases or whether they encourage “guilt-free” overconsumption.

Similar challenges exist in the circular economy and refurbishment. Take the case of refurbished electronics: is it always more environmentally friendly than a new product?

The answer is yes in the vast majority of cases, but the extent of the impact depends on numerous factors, including energy consumption during refurbishment, actual extended lifespan, return rates, transportation, usage patterns, and more.

Measuring the impact allows us to move from narrative to a real understanding of the effects generated.

Measuring to Build External Credibility

Externally, impact measurement also addresses a growing need for accountability and credibility.

Investors, partners, customers, and regulators now expect proof, not just commitments.

A structured measurement approach allows:

• highlight the impact generated for clients or the community
• to strengthen stakeholder trust,
• engage in dialogue based on facts,
• position the company as a serious and transparent player.

In an ecosystem where rhetoric is rampant, the ability to demonstrate one’s impact becomes a reputational competitive advantage.

How do you measure impact?

Start with the mission and the theory of change

Measuring impact is not about piling up metrics.

The first step is to clarify what the company is actually seeking to transform, and how its activities contribute to that change.

This involves formalizing a theory of change:

• what needs or problems are being addressed,
• what activities are being implemented,
• what results are expected,
• what impacts are sought in the medium and long term.
• which beneficiaries are targeted

This step is fundamental: it prevents us from measuring what is easy rather than what is relevant.

Choose useful, not exhaustive, indicators

Effective impact measurement relies on a limited number of meaningful indicators, tailored to the company’s stage of development.

The goal is not exhaustiveness, but the ability to:

• track changes over time,
• compare trajectories,
• inform strategic decisions.

These indicators can be quantitative or qualitative, direct or indirect, but they must always be linked to a concrete use.

A concrete example: Deuxième Avis, measuring to steer impact

The case of Deuxième Avis clearly illustrates how impact measurement can become a management tool.

The company, which enables patients facing complex health issues to obtain a second opinion for free, does not merely track its activity.

Specifically, Deuxième Avis has defined several mission objectives that it steers using specific indicators:

Maximizing the chances of recovery for patients with serious illnesses

• The number of potential beneficiaries and actual use of the service (opinions provided)
• Number of patients for whom surgery was avoided following the second opinion

Facilitate access to medical expertise for all patients

• The user recommendation rate and qualitative studies conducted several months after the opinion,
• the proportion of patients residing in underserved areas or medical deserts,
• the patients’ socioeconomic background and consideration of disabilities,

Transfer of medical expertise—acceptance by the medical community

• the proportion of consultations initiated on medical recommendation and partnerships with healthcare providers.

This approach helps identify gaps between theoretical access and actual usage, highlights blind spots (under-served populations, cultural or regional barriers), and enables continuous strategy adjustments.

Here, measuring impact serves not only to demonstrate social utility: it enables better decision-making and ensures the mission’s long-term coherence.

Integrating measurement into governance

To be useful, impact measurement must go beyond one-off reporting.

It benefits from being integrated:

• into governance bodies,
• into decision-making processes,
• strategic trade-offs.

Used in this way, it becomes a dynamic tool, serving overall performance and long-term consistency.

Embrace imperfection and make progress

Finally, measuring impact does not mean measuring everything perfectly from the start.

The process is inherently iterative: indicators evolve, understanding deepens, and indirect effects gradually emerge.

The key is to adopt a mindset ofcontinuous learning, rather than seeking a perfect measurement that is disconnected from actual practice.

In conclusion

Measuring impact is not about seeking reassurance.

It means being willing to test one’s intuitions against reality, identify blind spots, and steer a course over the long term.

At a time when impact is increasingly emphasized, measurement is no longer a methodological luxury: it has become a prerequisite for credibility and strategic robustness.

While some believe their mission will naturally follow growth, every trajectory—especially during a phase of acceleration—involves tensions. As an organization grows, its effects become more complex, sometimes counterintuitive. Without structured measurement, impact risks remaining at the level of a “good intention.” When well-designed, impact measurement therefore enables us to understand what actually works, to identify indirect or spillover effects, and to steer the strategy over the long term. It serves both as an internal decision-making tool and as an external lever for credibility and for demonstrating the generated impact to stakeholders.