Thus, if any particular campaign were made to reduce the cost for small orders by handling small orders on some different method from that previously used, the pins near the left-hand side of the board might appear considerably lower down on the chart than the pins of the color which had been used in the six months preceding the change in method.

When the board gets so full of pins as to make the pins crowded it is a very simple matter to remove from the board all of the pins which Avere inserted in the most remote period of time. Thus, it might be

FREQUENCY CURVES 195

found feasible to keep on the chart pins relating to four different periods of six months each, so that every six months one color of pins would be removed from the board and the pins removed would be those which had been placed in the board two years previously. A board would then show at all times the record of cost in handling this particular commodity during the last two years. Boards used where pins must be put in and taken out very often may be faced with cork composition so that the pin holes may injure the surface as little as possible. Where pins are not to be changed very frequently, the straw-board covered with a layer of cloth before the co-ordinate paper is mounted will be found entirely satisfactory.

In the upper portion of Fig. 159 is shown a summary chart of the data contained on the pin board itself. Curve "C" is a smooth curve drawn through the center of gravity of all pins on any vertical line which shows the size of order. It will be noticed that the cost decreases very little when orders become larger than three hundred packages, but for this particular commodity with the methods of handling used, the cost increases rapidly as orders decrease below three hundred packages.