The biggest US banks aren't going to be allowed to grow further through acquisitions of other banks. Therefore, they're going to have to master organic growth — holding onto the customers they have and persuading those customers to buy more products and services from them. That won't be easy: Big banks rank lowest on customer advocacy, which is the strongest driver of customer retention and future purchase consideration for financial services consumers. To improve their companies' standing with customers, channel strategy executives at big banks must master the four elements of customer advocacy: simplicity, benevolence, transparency, and trustworthiness.