Final answer:
The correct term for the percentage of customers leaving in one year is the 'defection rate.' It is crucial for businesses to track this rate to gauge customer retention and loyalty.
Step-by-step explanation:
The percentage of your customers that leave you in one year is known as your defection rate. This rate is an important metric used in businesses to understand customer retention and loyalty. It does not directly relate to the provided information about the 70th percentile or arrival times of customers, which is a separate statistical concept. To monitor and possibly reduce the defection rate, companies analyze customer satisfaction, quality of service, and other competitive factors that influence a customer's decision to stay with or leave a company.