Though Fig. 67 gives the data much more clearly and far more accurately than Fig. 66, the method is not satisfactory because it is difficult for the eye to follow the ends of the different bars in order to judge the increase made from decade to decade. The best method

GRAPHIC METHODS

I830

I840

I850

I860

I870

I504.

!280

164-7

IS90

ISOO

The Philadelphia Commercial Museum

Fig. 66. Commerce of the United States since 1830. The Sum of Annual Exports and Imports. Values are given in Millions of Dollars

Such a chart as this is worse than none. There is no scale in either direction. The block for 1830 is drawn with a larger area than the block for 1840 which represents a larger quantity. Compare with Fig. 67 and Fig. 68

CURVE PLOTTING

1630 t l34l

1B40 C

S22

reso C

. ^IG

"3

1B60 C

607 ■

Z3'

t870 C

S29

' 1

iBso r

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1690 r

.«47 •/■■-;.|

rsoo [

.,, Z24<|- • .-wv^a-.W :;,,.,]

Fig. 67. Values of Annual Exports and Imports of the United States. Figures are Given in Millions of Dollars

This chart is drawn to scale from the data given in Fig. CO, to show tlie use of horizontal bars for work of this nature

of the three is followed in Fig. 68, where the data from Fig. 67 are plotted in the form of a curve. The curve method brings out all the information in less space and in clearer form than does the block