When The Boston Consulting Group launched a study of five large digital display advertisers, new evidence of the power of data-driven approaches emerged. Such advanced techniques drove big performance gains – a 32% average decrease in cost per action – and enhanced both relevance and consumer experience by reaching engaged audiences at scale. The research advises brands to learn from digital’s wealth of data, address fragmentation in strategy, data, teams and tools, and to invest in "math men" and women to succeed.