Table 3 Rules for classifying KNR workers by process and number of men by process in Pedersen et al. (1973) [1] and Magnus et al. (1982) [2]

Categories of work

Rules allocating workers to processes

Roasting- smelting (R/S)

1) Cases and expected values (PYRs) for each process worker were classified to one of three processes (i.e. R/S, E or O) where he spent the longest time.

Electrolysis (E)

Other specified processes (O)

2) If he only spent some time in process work, but most of his time in non-process work (e.g. labourers, plumbers, fitters, foremen, technicians, etc.), then his experience was classified to the process (i.e. R/S, E or O).

Other and unspecified work (U)

3) If he worked in unspecified process work only, then his experience was allocated to that process (i.e. U).

Total