Are your customers truly faithful to you? Or are they seeing other people? It’s easy to assume that your clients bring you all their business. But how do you know for sure? It matters for at least two reasons. First, if they’re doing a little bit of their business somewhere else, that somewhere else is trying to persuade them to increase their commitment — at your expense. Second, if they’re straying, it means you’re leaving money on the table. So you need to know how much of their business your customers bring to you, what’s keeping them from giving you the rest, and what you need to do to keep the business you have and get the rest. The good news? It’s a lot easier — and cheaper — to win more business from existing customers than from other prospects.