(b) The principal factor in the calculation of the machine rate, in fact, the real key to a successful calculation, is in establishing a standard of work─hours for each machine. It is noted that the higher the standard, the lower will be the rate, and the lower the hours operated, the higher will be the rate; in other words, when the machine is idle in excess of the standard, the rate changes. In some shops where the output is a stable product, always in demand, and the machine in continuous operation, a good estimate may be made, but in most shops a machine is frequently idle on account of "no work" or "laid up" for repairs the same as is its operator. The practice in most shops is such that it is extremely difficult to estimate ahead what the work─hours of a machine will be, and it resolves itself generally into an intelligent guess with two estimators far apart in their estimates, yet a satisfactory distribution requires a standard which will work out in figures close to the actual facts. Who can successfully estimate ahead for any time the activity of each machine in a large factory? Our factory engineers are at wide variance on this point. One authority says "full time," 300 days a year, is the proper basis for calculation. It would seem as if this were rather an unusual position to take; it apparently being his belief that the time idle would be offset by the time the machine was operated overtime, or else he expected the machinery once put in motion to neither shut down, nor break down. Either appears to be rather a dangerous assumption on which to base a careful calculation for rate of distribution. Another engineer says 80% of a full day will be found to be the maximum, and further adds: "It will doubtless fall much below that figure." One naturally asks "How much lower?" There is quite a large field of figures to choose from between an 80% activity and a dead standstill for the machine. It is quite unnecessary to attempt to demonstrate at length that the work─hour standard may be a very elastic figure, and it is often found that after distribution has been made, the results are very unsatisfactory and the machine rates used have proved "way off." (c) Again, having settled on the work─hour standard, other adjustments appear necessary to equitably handle the machine rate question. For instance, two machines may be of the same book valuation and in cost of operation practically alike, yet one may be far more efficient than the other and possibly turn out two or three times as much work. This condition is constantly found in different shops, and whether or not the two machines should carry the same rate, and, if not, how this inequality shall be adjusted, forms a very interesting question for discussion.