Wim Vermeulen - The Science of Credibility
In conventional advertising, exaggeration is practically part of the job description. For decades, agencies have operated under a script perfected in the 1950s and 60s by industry pioneers like David Ogilvy and Bill Bernbach: dramatise the benefit. Take a product attribute, magnify it, and turn it into a compelling narrative.
Think of a standard toothpaste commercial. The voiceover confidently promises that your teeth will be crystal clear within two weeks. As consumers, we have spent a lifetime learning to decode this language. No one literally expects their teeth to replicate a diamond, and nobody returns a tube of toothpaste demanding a refund when they do not. We understand the unwritten rule: the benefit has simply been dramatised.
But when you apply that same 1950s advertising script to sustainability, the system completely breaks down.
I recently spoke with Wim Vermeulen, an award-winning strategist, author, and partner at the sustainable communication agency Bubka. Wim’s career began in traditional advertising, but six years ago, as the first wave of massive corporate sustainability campaigns began hitting the market, his gut told him something was fundamentally wrong. To figure out what, he teamed up with the University of Ghent to run a massive scientific study, testing 100 sustainability campaigns for effectiveness.
What they discovered exposes the fatal flaw in modern green marketing.
The Only Metric That Matters
When Wim and the academic researchers crunched the data from those 100 campaigns, they expected to find a variety of creative factors driving success. Instead, they found that effectiveness was almost entirely dictated by a single, monolithic variable: credibility.
Unlike conventional advertising, where consumers willingly tolerate exaggeration, sustainability communication operates under a zero-tolerance policy. Because sustainability campaigns are dealing with systemic, real-world crises like climate change and biodiversity loss, using the old "dramatised benefit" script triggers immediate scepticism.
If a brand overpromises or wraps its message in corporate hyperbole, the audience does not read between the lines; they simply stop believing. In sustainability, you are either credible or you are greenwashing. There is no grey area.
Introducing the Net Credibility Score (NCS)
To help brands navigate this high-stakes landscape, Wim and the University of Ghent developed a framework called the Net Credibility Score (NCS). Operating on a similar logic to the traditional Net Promoter Score, the NCS provides an objective benchmark for trust.
You measure the exact percentage of consumers who genuinely believe a campaign's narrative, subtract the percentage who do not, and the resulting figure gives you your benchmark.
The results across different European markets reveal a highly sceptical public. In Belgium, the average baseline benchmark sits at roughly 30. In the hyper-critical market of the Netherlands, the benchmark drops to just 15. If a sustainability campaign cannot score above these baseline numbers, it is not just wasting ad spend; it is actively damaging the brand's reputation.
Perceived Honesty vs Internal Intent
The core takeaway from Wim’s initial research is a brutal pill for marketers to swallow: honesty is not defined by your internal intentions; it is defined by consumer perception.
It does not matter if a sustainability team spent three years meticulously crafting a carbon-reduction initiative with the best intentions. If the final marketing campaign feels dishonest, exaggerated, or vague to the average consumer on the street, it is functionally dishonest.
In Part 2, we will look at why the corporate panic known as "greenhushing" is fueling consumer anxiety, and examine the six core indicators that determine whether the public will actually buy into your sustainability story.










