The importance of control groups for measuring marketing campaigns is well understood. However is it sensible to create a universal control group for marketing campaigns (almost similar) ? example- in a scenario there would be various loyalty campaigns on subscribers which would be governed by various internal marketing teams. Initially they all created control groups in silos and hence the campaign take rate was questionable. One solution is creating universal control group and uplift from it. However there is not a much buy-in on same. Pls suggest your views or links for further reading