The fact that the curves are all put into the same size of space on the curve cards causes them to have somewhere near the same percentage scale of height, even though the actual numerical scales may be widely different. Having all curves on the curve cards thus gives more accuracy and ease of reading than would be obtained if several curves were shown on large sheets of arithmetically ruled co-ordinate paper with one curve above the other to the same scale.

On the left-hand edge of each curve card shown in this chapter will be noticed the word "Authorized" with a space for a date and initials. When a new curve is added to the list of those curves which are regularly plotted in any organization, the man who desires to see the curve periodically must put his initials and the date of signing on the left-hand margin of the card. This is to show his approval of the general form in which the information is given, and to authorize the expense necessary in collecting data and plotting the curve week by week or month by month. A definite authorization, by which some one must sign his

CURVES FOR THE EXECUTIVE 285

initials in the manner described, assists greatly in preventing unnecessary clerical work, as it eliminates any curves which are not used somewhere in the organization. The man who approves the curve can be told just about what it costs to plot each curve. For instance, if three thousand dollars a year is expended for the labor, materials, etc., necessary in plotting all the curves in an organization, and there are three thousand curves kept regularly, it can be seen that the expense per curve per year will be about one dollar. Therefore, if the man should wish one hundred curves plotted for different data relating to his department, he would be approving an expenditure of about one hundred dollars per year.