Most marketers measure one brand well. L'Oréal measures more than 50 of them, across markets that behave nothing alike, and does it fast enough to change decisions while they still matter. At Cannes Lions 2026, Vasileios Kourakis, director of marketing effectiveness and measurement at L'Oréal, sat down with Circana’s Cara Pratt, president of global media and retail, and Emma Delserieys, senior VP of global media, to explain how that program came together over a partnership spanning roughly 20 years.
Here is a preview. The full conversation is worth your time.
Scale is not the hard part
You might assume the challenge of measuring 50-plus brands is the measurement itself. Kourakis reframes it. The models work. The difficulty is delivering speed and consistency across every market at once.
A number that means one thing in one country has to mean the same thing everywhere, or the whole program loses its footing. Accuracy without consistency produces conflicting signals. Consistency without speed produces answers that arrive too late to act on. L'Oréal set out to hold all three at the same time, at global scale.
Three principles hold it together
The program rests on three ideas, and none of them is a piece of software.
A complementary toolkit. Marketing mix models, brand lift studies, experiments, and conversion lift each answer a different question. Read together, they form one picture rather than competing ones.
A consistent process. One unified approach applied the same way in every market, so results compare cleanly across the portfolio.
A culture built on people. The measurement matters only when marketers trust it and act on it. Alignment at the human level is what turns analysis into decisions.
That last principle is the one most programs skip. Data and technology rarely hold an organization back. People and process do.
Creative carries more weight than most models admit
Here is the finding that should reorder a few priorities. Across platforms, creative drives roughly 40% to 50% of total ROI. Not targeting. Not placement. The work itself.
That has a direct consequence for how brands allocate attention. If half your return rides on creative quality, treating creative as a subjective afterthought is a measurable mistake. L'Oréal built the ability to measure it, which means the most emotional part of marketing now sits inside the same accountability framework as the rest.
There is a companion insight, drawn from joint research with Meta:
"Branded and creator content together can improve results by up to 35%."
The two formats are not substitutes. Combined, they compound.
The long game, measured
Short-term ROI is seductive because it is easy to see. It is also a trap. Optimize only for the near term and you quietly spend down the brand equity you spent years building.
L'Oréal addresses this with a long-term multiplier, developed alongside Circana, Google, and Professor Mela at Duke University, and built directly into its A&P optimization. It lets marketers weigh short-term performance and long-term equity in the same decision rather than choosing one over the other.
The timing data makes the stakes concrete:
Cut investment materially, and equity and sales erosion begin in about four weeks.
Rebuild that impact, and a marketing playbook typically needs 6 to 13 weeks to move the needle.
Erosion is fast. Recovery is slow. That asymmetry alone is an argument for measuring the long term as carefully as the short.
AI that serves the marketer
Kourakis is direct about where AI fits, and where it does not.
"Measurement is there to serve marketers, not replace marketers."
AI runs across the end-to-end process at L'Oréal, but as an instrument for better decisions, not a substitute for the person making them. For a company founded by a scientist yet built on emotion, that balance is not a slogan. It is how the work gets done.
Watch the conversation
The full interview covers how L'Oréal turned marketing effectiveness into a competitive advantage, why creative deserves a seat in the measurement framework, and what still keeps effectiveness leaders thinking on their morning treadmill.
Watch the full conversation with Vasileios Kourakis and Cara Pratt and Emma Delserieys from Cannes Lions 2026.
Behind the program sits Circana, the long-standing measurement authority that helped L'Oréal scale accuracy and consistency across its global portfolio. Explore Circana's marketing effectiveness solutions to see how measurement becomes a decision you can act on with confidence.
