We isolate the true impact of media investment, separating what it actually drove from demand that would have existed regardless, so leadership has the causal proof to make confident budget decisions.
How does January Digital approach incrementality testing?
Attribution tells you who claims credit. Incrementality tells you who earned it. Every platform overcounts because every platform measures conversions that would have happened without the ad. Incrementality testing is the only way to know if media is driving net-new revenue or simply taking credit for demand that was already there.
We split audiences into exposed and control groups, run the media flight, and measure the true revenue difference between them. The output is iROAS, the actual return on each incremental dollar spent, not a platform-reported number.
What incrementality testing methods do you use?
We use geo-based holdout tests and synthetic control methodology depending on the measurement challenge. Geo holdouts split geographies rather than users, which allows for robust causal inference without requiring personal data or user-level tracking. Synthetic control methodology combines and weights geographic regions to simulate a user-level study, giving statistically precise results even in a privacy-constrained environment.
Test design matters as much as methodology. We structure test cells to avoid overlap with promotions, product launches, and localized marketing to ensure results are valid and actionable.
How do you approach budget reallocation based on test results?
Once we have iROAS by channel or tactic, the reallocation decision becomes straightforward. Channels with high incremental return get more investment. Channels taking credit for organic demand get less. We build the reallocation recommendation alongside the test results so leadership has both the proof and the plan in the same conversation.
For a digitally native apparel brand, reallocation based on incrementality test results drove a 6% beat on their Marketing Efficiency Ratio goal the following month.
When does incrementality testing make the most sense?
Incrementality testing is most valuable when a brand is about to scale a channel and wants causal proof before committing budget, when platform ROAS looks strong but business results feel soft, or when finance is questioning whether media is actually driving sales. We scope any test in 24 hours.
What results has January Digital driven for clients through incrementality testing?
For a digitally native apparel brand, Nonbrand Performance Max delivered approximately 5x higher iROAS than Meta Prospecting Conversion, leading to a budget reallocation that beat their MER goal by 6% in the following month. For a luxury fashion brand, Performance Max achieved an iROAS of $2.66, exceeding benchmark by 39%, while Meta ASC achieved an iROAS of $2.46, exceeding benchmark by 30%, enabling reallocation across tactics representing 65% of total July budget. For a leading retail property company, ad recall campaigns drove incremental traffic at more than 90% lower cost than traffic campaigns, performing over 16x more efficiently.