Incrementality Testing

What Is Incrementality Testing?

Classic attribution models often overestimate the contribution of advertising because they confuse correlation with causation. Incrementality Testing solves this problem and shows you the true advertising impact. For sound budget decisions in performance marketing, this method is indispensable — it can reveal that certain campaigns achieve less (or more) than expected.

Incrementality Testing is the overarching methodology for determining the actual added value of your Google Ads campaigns. At its core, it answers the question: how many conversions would have happened without your advertising? This question is critical because classic attribution systematically overestimates advertising success by attributing conversions to ads that would have happened anyway.

There are various methods for Incrementality Testing. The strongest is the Holdback Experiment, where a control group sees no ads. Alternatively, you can use Causal Impact analyses that statistically derive advertising success from time series data. Google offers its own tool with Conversion Lift that enables incrementality tests directly within the platform.

In practice, it is advisable to run incrementality tests at least once per quarter for your most important campaigns. Start with brand campaigns, as incrementality is most frequently overestimated there. Use the results to shift budgets from campaigns with low incrementality toward campaigns with high incremental value. This way you optimize not for attribution, but for real business success.