You're both right, _and_ wrong, because people, firms, and their respective behaviors vary a ton. Some marketing teams are great at measuring the effect of thei

You're both right, _and_ wrong, because people, firms, and their respective behaviors vary a ton. Some marketing teams are great at measuring the effect of their ad spend. Some are not. It depends on the specific circumstances and the specific humans involved. I'd be interested in an argument over whether more marketers are competent versus not, but any argument that presupposes uniformity among marketers is just silly.