Medically certified absence (absence from work attributed to disease and accident) is an important and convenient index of workers' health and attitudes. It also constitutes the largest part of total absence from work. Depending on the country and on industry and population characteristics, sick-leave accounts for 60-70%, and injuries for another 7-20%. The balance is defined as "healthy-worker absence", taken with or without prior permission or post-facto justification. It is characteristic of the first and last phases of an employee's history at the firm; either before he has time to become a permanent employee and adapt to the local "absence culture", or when he contemplates leaving. On the other hand, certified absence is confirmed by a higher authority, and so it is accepted by management, the insuring institution, and the peer group (which often have to carry the extra workload). This absence belongs to the phase of regular relationships, which both sides seek to maintain. Whether and how often the employee has recourse to certification depends on a number of factors. Those mentioned most often in the literature are: (a) absence--proneness-apparently a defined personality trait (psychological or psychosomatic) leading to repeated absences; (b) poor working conditions; (c) lack of group cohesiveness--members of a well-structured group are upheld by its solidarity and sense of belonging ("esprit de corps"); this is observed in smaller and more closely-knit groups such as shift and group teams, as in the Volvo experiment; (d) quality of the leadership and organizational behavior; (e) job satisfaction--deprivation of recognition, use of abilities, responsibility, and interest have strong psychosomatic repercussion; (f) interaction with external forces, especially marketplace conditions--lack of external demand may restrain absence.