Weighting the bars by showing volume as well as price gives a more accurate picture than a simple bilateral chart would Rive. However, a representation of volume is not always necessary.

AREA BAR CHARTS

CHARACTERISTICS OF AREA BAR CHARTS:

1. Useful in presentinj; material which ^ivcs parts of a total.

2. They show in one view two independent {groups of facts.

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National Industrial Confcrcncr Board, Inc. N Y. C, February 11. 1937 Proportion of the Working Population Covered by the Old Age Provisions of the Social Security Act in the United States, Using the Distribution of Occupations of the 1930 Census.

1. Not only the percentage covered or not covered by old-age provisions of the Social

Security Act is presented, but also the percentage of the total working force of each of the types of labor.

2. If only the percentage covered in each type of industry were given, the representation

would be obviously false.

GRAPHIC PRESENTATION

Massachusrtts Institute of TechnoloRy, "The. Technology Review." February 1933.

Occupational Distribution in 1930 of 134 MIT Graduates of the Classes of 1917 to 1929 Inclusive.

1. This chart is in reality a group of 100% bar charts. It was placed in this chapter

because of its resemblance to the preceding charts.

2. The emphasis on the area for "Major Executive" tends to make the comparison a