olemus
(a) klientuuri vähenemine või vahetumine
(b) tööjõu vahetumine

Merriam-Webster:
2: a regular, quantifiable process or rate of change that occurs in a business over a period of time as existing customers are lost and new customers are added
// The biggest problem they face is churn. Wireless providers lose an average of about 30% of their customers a year to competitors.
also : a similar process or rate of change involving loss and addition of employees, companies, etc.
// the resulting employment churn—the average job tenure is now two years, and today's typical 32-year-old has held nine different jobs—means more risks as well as more opportunities to discover new paths.

ülevaateid
https://en.wikipedia.org/wiki/Churn_rate