If you spend any time in affiliate and performance marketing conversations right now, one word keeps resurfacing: incrementality.
It appears in pitch decks, budget meetings and internal channel debates. Everyone claims to drive it. Everyone says they can prove it. Almost every proposal positions itself as the incremental solution. And yet, very few people seem to define it in the same way.
Having worked on the brand side, I have learned that incrementality is rarely an academic debate. It is usually a financial one. When budgets tighten, incrementality becomes the justification. When channels compete internally, incrementality becomes the argument.
The problem is not that incrementality matters. It absolutely does. The problem is that we often treat it as a label rather than a measurement.
In affiliate, incrementality has traditionally been framed around a simple question: would this conversion have happened anyway? That question drove years of debate around last click attribution, voucher usage and brand bidding. We built frameworks to isolate uplift, sometimes successfully, sometimes less convincingly. But even then, the baseline was often unclear.
Incrementality only makes sense when the counterfactual is defined properly. What would have happened without this activity? Would the customer have purchased anyway? Would they have chosen the same product? Would the margin have been identical? Would another channel have captured the demand? Too often, we skip that clarity.
Instead, we measure performance and assume it represents new value. We point to conversions, revenue lines and reported uplift without fully interrogating what would have occurred in the absence of that activity.
That is where the illusion begins.
If every channel, partner and placement describes itself as incremental, the word gradually loses meaning. It becomes a defence mechanism rather than a discipline. A way to protect budget rather than test commercial truth.
Working across performance environments, I hear incrementality referenced constantly. What I hear far less often is a clear explanation of the baseline being used to measure it. Without that baseline, we are not measuring incrementality. We are measuring activity.
True incrementality should feel slightly uncomfortable. It should challenge internal assumptions about substitution effects, margin erosion and channel overlap. It should force alignment between marketing, commercial and finance teams on what genuine net new value looks like.
Incrementality is not a slogan. It is a counterfactual question. Until we get more consistent about how we define and measure it, we will continue to debate it endlessly, each side confident they are right, while operating from entirely different assumptions.
The industry does not need more claims of incrementality; in fact, a completely different take: it needs fewer illusions and clearer baselines.
