The amount of new employees hired within a certain time frame to replace employees who have quit or been fired.
Insurance Encyclopedia
Turnover rate
Number of times employees terminate employment other than by death (i.e., they’re fired, they resign, or they retire) and are replaced. This is a factor that affects the cost of a retirement plan.
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US: The rate at which employees terminate covered service other than by death or retirement. Expected future turnover can be taken into account in translating contributions into benefits.