Did the new content channel grow the pie, or just eat the organic slice?

Did the new content channel grow the pie, or just eat the organic slice?

A publisher launched a content-marketing push, watched last-touch credit accrue to it, and called it a win. The sharper question: were those conversions new, or migrated from organic search the brand was already winning for free?

The analysis. The team paired last-touch attribution with a cannibalization check — comparing total conversions before and after launch against a synthetic-control baseline (a weighted combination of comparison periods/markets engineered to mimic the pre-launch trend). This isolates net-new conversions from credit that simply migrated between owned channels.

What it showed. Last-touch reported the content channel "driving" a healthy conversion volume. The synthetic-control comparison revealed total conversions barely moved — a documented pattern where a large majority of the new channel's attributed conversions were cannibalized from organic and direct, paths the brand already owned. Net incrementality was a fraction of the attributed figure.

The nuance. Attribution distributes credit among channels but is blind to whether the total grew. A channel can dominate the credit report while adding nothing to the top line, because it intercepted journeys headed to a free channel. Correlation with conversions is not contribution to conversions.

Bottom line for practitioners: judge a new owned channel by movement in total conversions against a synthetic-control or holdout baseline, never by the credit attribution hands it. The question is whether the pie grew, not which slice got labeled. In the documented case, the channel was mostly relabeling demand the brand already captured for free.