Incrementality refers to the additional results you get from a marketing activity that wouldn’t have happened without it. If you run a Facebook ad campaign and get 100 sales, the incrementality question is how many of those sales were actually caused by the ads versus people who would have bought anyway through other channels. True incrementality means you’re generating new outcomes, not just taking credit for things that were going to happen regardless. Understanding incrementality prevents you from over-attributing results to specific channels and helps you make better budget allocation decisions.
Why Attribution Lies About Incrementality
Most attribution models give channels credit for conversions they influenced but they don’t tell you if those conversions were truly incremental. Someone might click your Facebook ad, then Google your brand, then buy. Facebook gets credit. But maybe they were going to Google you anyway because they saw your organic content earlier. The Facebook ad wasn’t incremental. It was just the last touch before something that was already going to happen. This matters because if you think Facebook is driving 100 incremental sales but it’s really only driving 30, you’re going to make bad decisions about budget allocation.
Testing For True Incrementality
The only way to really know incrementality is through holdout testing where you compare results in groups that saw your marketing versus control groups that didn’t. If you turn off Facebook ads for a random segment and sales drop significantly in that segment compared to the segment still seeing ads, you have proof of incrementality. If sales barely change, the ads weren’t driving incremental results. Most businesses never test this which is why they waste budget on channels that aren’t actually driving growth. The sophisticated companies test incrementality regularly and shift budget away from channels that are taking credit without driving true incremental results.