Note the co-ordinate paper of letter-sheet size and the scheme for marking off weeks and months so that any fiscal year may be shown on this standard ruled paper

from the engineering department, the factory was able to ship practically no cars during the month of January, though the schedule shows that one hundred and fifty cars should have been made that month. During February, the factory produced cars but fell further behind schedule constantly, as can be seen by the difference between the angle of the schedule line for February and the angle of the actual output line for February.

It must be remembered that with cumulative curves the angle between the curve and the horizontal line gives the rate of production per unit of time. The angle of the curve on the page gives much valuable information to the reader. It is for this reason that cumulative curves are sometimes much more useful than curves in which the rate of output is plotted horizontally from time to time. In the cumulative curve the total output is plotted, and changes in the rate

CUMULATIVE CURVES 151

of output, judged by the angle of the curve at different times, may be seen very easily.

During March the output curve took a rapid upward turn and we can see from its angle that, until the end of the first week in xA.pril, the output curve gradually approached the curve for schedule. During the latter part of March the factory not only got out its quota of cars each week but produced more than its quota, making up a little for the distance it fell behind during the first part of the year. Owing to a lack of material, because of a fire in a factory which supplied the crank shafts for the automobiles, not a single automobile could be shipped during the second week in April and only a few in the third week of April.