Why last click attribution CPA can be misleading

It’s Black Friday. Your CPA drops from £/€ 20 to £/€ 10.

Have I become a marketing genius? Is the creative suddenly resonating better? Did I finally nail the audience?

Were there just more people in-market to buy?

That’s the trap. Too often, teams judge marketing performance by last-click CPA. But often last-click attribution reflects purchase behavior, not marketing impact. It gives credit to the channel closest to the conversion, ignoring everything that built awareness, trust, and intent along the way.

What drives the wild changes in CPA?

• We created demand. Brand, product, or upper-funnel activity did its job before the last click.
• Underlying demand increased. The market itself drove more people to purchase (think Ice cream on a sunny day)

📉 The risk? You undervalue the work that drives demand, and over-invest in the channels that simply close it.

📈 True marketing impact needs a broader lens. MMM & incrementality testing uncover what really works. Too often, these tools have only been available to Enterprise brands however, Linea’s measurement tools are allowing Brands of all sizes to run MMM & A/B tests.

Long-term growth comes from an accurate understanding of what's growing your business.