IT is sometimes forgotten that output results from human activity and that therefore the amount will be dependent on many factors, of which it has been shown that the number of hours worked each week is one. There is abundant evidence that excessive hours result in diminished output. When, however, hours are relatively reasonable, can it be argued that a further reduction will increase the output? A recent report ("A Study of Variations in Output." By S. Wyatt and others. Emergency Report No. 5 of the Industrial Health Research Board.(London: H.M. Stationery Office, 1944.) 4d. net.) analyses some of the factors which had measurable effects on output. Study of the output records of a number of factories showed a striking variability. Some of the chief causes were: (a) changes in the type or design of the product; (b) mechanical difficulties and machine breakdown; (c) variations in the quantity and quality of the materials used; (d) progressive improvements in the methods or conditions of work; (e) changes in the type and lay-out of machines; (f) personal factors such as dissatisfaction with the methods or rate of payment, and occasional friction between the management and the workers.