Your strategy for tracking attrition will be based primarily on your business type. For example, it is easier for public relations firms to track this metric than retail stores. However, there are ways around any challenge that may come your way.
For a service based business, such as a public relations firm, all you need is a list of active clients. From there, you will track clients that leave your firm while also adding new ones as contracts are secured.
Now do you see why it is so important to track customer attrition? This really does matter to the future success of your business.