Just because the curves in the upper portion of the chart represent numerically larger quantities, they have much more vertical movement up and down on the face of the chart than those curves in the lower portion of the chart which may have an even greater amount of percentage fluctuation. This wide difference in the amount of vertical movement on a page is one unfortunate source of confusion to persons who are just beginning to study curve charting.

Fig. 123 is plotted from the same data as Fig. 122, but it is on paper having logarithmic spacing for the vertical scale with the ordinary arithmetical spacing for the horizontal scale. With the logarithmic spacing on the vertical scale the fluctuations in the different curves show in true proportion. Curve F appeared insignificant in Fig. 122 because it happened to fall near the bottom of the chart where percentage fluctuations are not prominently shown. In Fig, 123, however, curve F shows up as having far the greatest percentage changes of any curve on the whole chart. For persons who understand even slightly the principles involved in reading charts plotted on logarithmic paper. Fig. 123 shows up the facts in much more convenient form than Fig. 122. To make comparison most convenient, the two figures are placed on facing pages, 134 and 135.

GRAPHIC METHODS

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