Deaths in Boston of Children under Five Years of Age, under One Year, and from Five of the Principal Infectious Diseases, Expressed as a Percentage of the Total Mortality

Curve A. Deaths of children under five years of age as a percentage of

the total mortality Curve B. Deaths of children under one year as a percentage of the total

mortality Curve C. Deaths from Diphtheria, Scarlet Fever, Measles, Typhoid Fever

and Smallpox as a percentage of the total mortality Note that Curve A shows a much steeper slope than Curve C, yet Curve C

drops in 1910 to less than half the figure for 1871. Curves plotted by

rectangular co-ordinates should not be compared by the slope of the

different curve lines

The reader is apt to overlook the fact that the vertical scale of the chart does not extend below $11 per ton. He is quite likelj^ to think that the price of pig iron had all the rapid fluctuations which would be indicated by the changing vertical distances between the pig-iron curve and the bottom line of the chart itself. The amount of fluctuation would look much less if the chart extended to the zero line of the vertical scale.

GRAPHIC METHODS

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