AbstractIn manpower planning, it is essential to be able to monitor stability of the length-of-service structure of the staff. Such a stability index is provided by the formula for entropy of a continuous distribution, evaluated for length of service. This measure improves on the previous discrete version by removing the necessity of introducing arbitrary tenure classes, thus facilitating inter-company comparisons. It is closely related to the entropy formula used in demography, and manpower planners may therefore avail themselves of results already used by demographers.