Marketers have always railed against the idea that it is impossible to tell whether, and what part of, their spending drives sales. Even when everything was analog, Nielsen set-top boxes and Arbitron radio diaries — panel and survey data — provided insight.
The dawn of digital media promised a brighter future, where we eventually could look at every sale and determine which touchpoints were effective at delivering ROI and which were wasted spend. It’s not nearly as simple or straightforw…