“…For example, it became clear in subsequent work that the point* b had been assumed to be fixed in the original empirical work and yet, the institutional interpretation indicates quite clearly that b should move to the left as normal hours of work, H N , are reduced [14]. Again, in subsequent work, it also became clear that because of the existence of "quasi-fixed labour costs" (i.e., costs that vary with the number of employees and not with hours of work), the minimum point, b, will not occur at normal hours [15]. Such factors as lump-sum National Insurance Contributions will tend to make H* > H N and give rise to the possibility of permanent overtime working.…”