The document describes Left Brain Marketing Planning, a new approach to marketing resource allocation that is customer-focused, data-driven, and aims to deliver high returns on investment. It notes that traditional marketing planning fails to account for changing consumer behaviors and media consumption. Left Brain Marketing Planning uses analytical tools and experimental design principles to determine which marketing resources best influence customers at different points in their purchase journey, rather than focusing primarily on media buys. Examples of companies adopting aspects of this approach are provided.