The argument for greater use of permanent night shift does not match the three times greater use of rotating three-shift systems in Britain. Studies of industrial production show very slight differences between output on different shifts, unlike laboratory studies, suggesting that it is almost impossible to reproduce the practice, motivation, and real consequences of work in laboratory settings. People who prefer permanent night shift often prefer to avoid management, and few managements welcome this; or have important tasks to perform at home in the day-time. Some studies of adaptation have defined inversion of temperature curves poorly, and most night-workers never completely adapt. Social flexibility, which has been the main attraction of rapidly rotating shifts, can be reproduced on permanent night shifts, but then loses the possibility of adaptation.