Shrinkage accounts for everything that keeps a scheduled agent off the queue: breaks, training, meetings, coaching, sick days, admin, and no-shows. It is the number that separates "how many people are on the payroll" from "how many are actually answering customers right now," and forgetting it is the classic way to under-staff a team.
The formula is unavailable time divided by total scheduled time.
What it hides: not all shrinkage is waste — coaching and training are shrinkage that pays off later. Cutting it indiscriminately to hit availability targets starves the development and recovery that keep quality and retention up.