Understanding Incrementality: Measuring True Campaign Impact

In today’s post-privacy landscape, traditional attribution models no longer provide the clarity marketers need to evaluate campaign success. The shift away from user-level tracking, driven by privacy regulations like GDPR and Apple’s App Tracking Transparency, has created a significant gap in performance measurement. Enter incrementality testing — a method that offers clarity, precision, and genuine insight into what’s really driving user behavior. For data-driven marketers, incrementality testing has become the gold standard for evaluating true campaign effectiveness.

What is Incrementality?

Incrementality refers to the additional value generated by a marketing campaign compared to what would have occurred naturally, without any advertising. It answers a fundamental question: Did this ad truly cause the user to take action — or would they have converted anyway?

This approach moves beyond vanity metrics and seeks to understand causality. Instead of relying on attribution models that track clicks or views, incrementality digs deeper to determine if a campaign actually influenced behavior.

For instance, if a user installs an app after seeing an ad, incrementality testing helps determine whether that action was driven by the ad or if the user was already likely to install the app regardless.

Why It Matters

Many attribution tools rely on heuristics like last-click, first-touch, or view-through models. These models often over-credit ad platforms by ignoring organic behavior and natural conversion tendencies. A campaign might look successful on paper, but in reality, many of the conversions may have happened with or without the ad exposure.

Incrementality testing removes this bias. By comparing exposed users to a control group that did not see the ad, marketers can identify the true lift — the incremental value attributable to the campaign. This insight allows for better budget allocation, channel optimization, and overall marketing strategy.

Moreover, as platforms limit cross-site tracking, traditional multi-touch attribution becomes less reliable. Incrementality doesn't rely on user-level identifiers, making it a future-proof solution.

How to Run an Incrementality Test

Running an incrementality test involves careful setup and a scientific mindset. Here's a simple framework:

1. Create a Control Group
   Select a representative sample of your target audience and exclude them from seeing your ad. This group should mirror the demographics and behavior of your ad-exposed group.
   

2. Run the Campaign Normally
   Serve the ads to the rest of your audience as planned. Make no changes to the creative, targeting, or bidding strategies to maintain consistency.
   

3. Measure the Difference
   After the campaign period, compare outcomes — such as conversions, revenue, or app installs — between the exposed group and the control group. The difference represents your campaign's incremental lift.
   

4. Analyze and Iterate
   Dig into the data to understand what worked and what didn’t. Segment results by audience, geography, or channel to uncover deeper insights.
   

Real-World Example

Consider a mobile game developer who wanted to evaluate the impact of rewarded video ads. They set aside 10% of their user base as a holdout group that saw no ads. After a four-week campaign, they discovered that users who were shown the ads generated 27% more revenue than those who weren’t. This test helped them confidently increase spend on that ad format, knowing it was genuinely driving growth.

Final Thoughts

In an era where privacy constraints limit traditional tracking, incrementality testing offers a reliable, privacy-compliant way to measure what truly works. It forces marketers to move away from assumptions and toward evidence-based decisions.

Whether you're scaling ad budgets or exploring new channels, incrementality testing should be a core part of your measurement strategy. It’s not just a best practice — it’s an essential tool for modern marketers aiming to prove real business impact.