> You need an experiment to prove that ad spending scales with ROI, as ad agencies claim There is a limited audience that can be influenced. Just like house ad

> You need an experiment to prove that ad spending scales with ROI, as ad agencies claim There is a limited audience that can be influenced. Just like house ads on a site (where you advertise to sell your own goods on your own site), there's only so much that is affected because you have finite traffic. There is a curve for every permutation of context (demographic, geographic, etc).