Business Metrics
Churn
The rate at which customers stop doing business with a company, typically expressed as a percentage of customers lost per time period. The inverse of retention.
Biological Context
Churn parallels mortality rate in populations. Just as populations need birth rates exceeding death rates to grow, businesses need acquisition exceeding churn. High churn indicates poor 'habitat quality'—customers are leaving because their needs aren't being met.
Business Application
Small reductions in churn compound dramatically over time. A 5% monthly churn means losing half your customers in a year. Retention economics often dominate acquisition economics for subscription businesses.