Search remains the No. 1 digital tactic to acquire customers, but attribution modeling hinders attribution and makes the whole process messy. In the 2014 Shop.org and Forrester Research State Of Retailing report, marketers cite several challenges with attribution models. While technology, analytics and organizational hurdles contribute to challenges, the biggest problem remains the inability to recognize consumers across devices and connect the data. Without the proper model, marketers cannot reallocate the amount they spend.