Page:Graphic methods for presenting facts (1914).djvu/59

 dates placed always at the base of the chart.

Another difficulty in the comparison of areas is shown in Fig. 39. No figures have been given and the helpless reader must compare by means of the pictures alone. By measurement, it will be seen that the minister in 1700 has over three times the height of the minister in 1900. Since the man in each case is shown in his natural proportions, the picture of the minister in 1700 has over nine times the area of the picture for 1900. Whether the ratio should be roughly three or roughly nine, we cannot tell.

World's Work

Fig. 40. Passengers Carried on the Railroads of the United States in 1899 and in 1911 Compared

This illustration has all the bad features mentioned for Fig. 39. Here the numerical data are given and we can prove for ourselves that the two pictured men are compared on the basis of height. Because of the disproportionate area, the right-hand picture gives the reader a false and exaggerated impression of growth. See Fig. 41

Fig. 41. Number of Passengers Carried on the Railroads of the United States in 1899 and in 1911 Compared

Here is a chart drawn from the same data as Fig. 40. It was not a larger passenger, but more passengers, that the railroads carried. The ratio expressing increase in business can be clearly and accurately seen from this method of portraying the facts

Another example of the same kind of difficulty appears in Fig. 40, but here the figures are given and we can check up the author to see whether he has drawn the 1911 man on the basis of height or on the basis of area. The 1911 man, on account of his far greater area, looks to be rather more than two and a quarter times as important as the man of 1899. Though this type of graphic work is quite common, it should be avoided, for its visual inaccuracy is serious enough to cause distrust of the whole graphic method. In considering Fig. 40, the point