For absolute spend ROIs and the like, we typically prefer building market mix models these days though we keep experimenting with others. On our scale, quality

For absolute spend ROIs and the like, we typically prefer building market mix models these days though we keep experimenting with others. On our scale, quality of targeting is something we trade off vs reach. The relationship is often non linear - say you get 10 million reach at an expensive CPM but very high accuracy vs. a 100 million reach that is cheap CPM but has half the accuracy, we'd might be better off putting money in the second bucket.