It is not until after a considerable amount of puzzling that one notices that the triangles have absolutely no significance and that they are only a means of showing the distance from the base line to the various points representing decrease or increase. It would have been better if plain black bars had been used for Fig. 148 instead of the triangles. Bars are so familiar to everyone that there would be no danger of error in interpretation. This illustration was used in a Sunday newspaper article where a non-technical class of readers had to be reached. For such a class of readers the solid black bars would probably be the most easily understood method of presentation.

For anything except newspaper presentation, the method of Fig. 149 would probably be more acceptable • to the reader than the solid black bars suggested in the preceding paragraph. The curve drawn in Fig. 149 shows a fairly uniform increase in death rates as ages increase up to the age of sixty. The degree of uniformity in increase is much more readily seen from the curve line than it could be shown

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Fig. 147. Comparative Proportion of Deaths at Different Ages from Pneumonia per 1,000 Deaths from Pneumonia in the Registration Area of the United States, 1890 and 1900