Page:Graphic methods for presenting facts (1914).djvu/370

 New York Times Annalist

Fig. 244. Average per Capita in the United States of Total Savings-bank Deposits

At first glance the impression is that Americans are growing rich very rapidly. Yet total deposits per capita have not doubled in the sixteen years shown. If the bottom line of the chart were at the zero of the vertical scale, an entirely different impression would be given. See Fig. 245

At numerous places throughout this book criticisms have been made of curves and charts in which no zero line for the vertical scale was shown on the chart. Though this subject has been mentioned elsewhere it seems best to show here a few examples on the same general argument. In Fig. 244 the first glance impression that savings-banks deposits have increased with great rapidity is not entirely confirmed when it is noticed that the left-hand scale does not begin anywhere near zero. It is nearly always possible to make a chart so that the zero of the vertical scale will show. Usually, of course, the zero line is at the bottom of the chart unless there are negative quantities so that the curve crosses over the zero line and extends below it. In all cases the zero line can be made a heavy line. If the curve should extend below the zero line the width of the zero line should be so great that the reader will be certain to interpret the chart from the zero line rather than from the bottom line of the chart itself.

Fig. 245. Average per Capita of Total Savings-bank Deposits in the United States

Whenever possible a chart containing curves should be so drawn that the zero of the vertical scale appears in the chart. If the zero line is not shown on the chart, that fact should be indicated by a wavy line at the bottom warning the reader that interpretation must be made from the vertical scale and not by visual measurement from the bottom line of the chart

It sometimes happens that the data for a chart involve high numerical figures so that a large amount of space must be used if the zero line of the vertical scale is to be shown in the final illustration. In such a case, the bottom of the chart may have a wavy line as seen in Fig. 245 which portrays the same data as Fig. 244. Fig. 244 could have been extended so that the bottom line would be the zero line if a