Fig. 25 shows a chart of the same data from which Fig. 24 was drawn. It is readily seen that it would be impossible for the average reader to tell whether this chart was drawn on the basis of height or the basis of area. The pigs of copper are not of the same size in the different piles, and it is evident that a pictured pig of copper is not intended to be the unit. If Fig. 25 is drawn on an area basis, it is almost impossible for the eye to fit the area for the right-hand pile into the area of the left-hand pile. This chart is a typical example of thousands of illustrations used by the popular magazines and even by some of the more pretentious reference books.
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Philips' Chamber of Commerce Atlas
Fig. 26. A Year's Production of Tin in Tons
This illustration, taken from the same source as Fig.
25, is even more confusing. The perspective of
the tops of the pigs of tin is such that there is
no way of telling whether visual comparison
should be made by height, area or volume
Fig. 26 is an even greater atrocity than Fig. 25. In Fig. 26, the observer is entirely unable to tell whether comparison is made in one, two, or three dimensions and he has an additional puzzle because of the large amount of perspective shown for the top of the pigs of tin. It would be surprising if one man in a thousand could guess anything near the ratio intended to be expressed between the largest and smallest pigs shown. In general, graphic work of this kind is much worse than the use of figures alone. There are times when an absence of knowledge is better than incorrect knowledge.
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Fig. 27. Value of Cotton and of Wheat Produced in the United States in 1910
Here is a suggestion for a standard arrangement for
horizontal-bar comparisons. The illustrations
at the left make the presentation popular in
form, yet actual figures for the data are given
at the left-hand end of the bars
Fig. 27 is a good example of what can be done as a standard arrangement for simple comparisons. On the left there is a symbol to attract the eye and interest the observer. Note that a dollar mark is shown on top of the picture of the bale of cotton in one case and the sheaf of wheat in the other, to indicate that the value of the crop is considered rather than the number of units. After the pictures, which may be thought of as "eye catchers," we have the figures, and then the bars plotted to scale for quick comparison by the reader. This cut could have been improved slightly if the spaces between the sep-
