Brian Lesser was promoted to run GroupM in North America last year after building its Xaxis trading desk into a billion dollar business. "My job is to transform GroupM to be much more about gathering data about consumers, because that's where our leverage is going to come from in the future." In this inaugural AdExchanger Talks podcast episode, Lesser discusses the evolving transparency debate, GroupM's ad tech investments and changes to the holding company model.  Episode sponsored by Google.