Attrition is a Key Performance Indicator that measures the value of lost business. It tracks the sales activity of lost customers who bought last year but not this year. The goal is lose less customer value than what is either retained or acquired.

When Attrition is more than either Retention or Acquisition, it is a sign of trouble that can be corrected either by reducing Attrition or increasing Acquisition. Note that reducing Attrition is estimated to be ten times less costly than increasing Acquisition. One of the best ways to reduce Customer Attrition is to monitor their Expectancy and to offer them incentives to buy again when then enter into negative Expectancy territory. Monitoring the Expectancy of very high value Customers and interacting with them before then enter negative Expectancy can be especially effective in reducing their Attrition.

The Attrition Rate is the sales activity of this year's lost customers, i.e those who bought last year but not this year, divided by the sales activity of all of last year's customers.