The time series comparison of index numbers in bar form is here supplemented by

actual figures. Thus anyone consulting it is able to quote figures without computing the various heights.

2. However, the figures placed at the top of each bar add to its visual length, resulting in

a false visual comparison. A better position for the figures would be between the date and the bottom of the bar, or in the form of a data table below the chart.

3. For explanation of index numbers, see 30 1 A

Chapter 13 CONTRASTING BAR CHARTS

ONE VARIATION of the type of bar chart shown in Chapter 12 is to differentiate the bars by using hachures. or shadings. Charts in which this technique is used are called contrasting bar

charts.

Green Giant brand peas

Other Peas

Green Giant pack increased 400% over 1930.

Selling price ot Green Giants decreased 12 1/3% since 1930. 1932

Advertising cost on Green Giants per case decreased 29% since 1930.

Minnrtota Valley Canning Company, Beaver Dam , Wis., "Annual Report for the Fiscal Year Ended March 31, 1938."

A. A Comparison of the Shipmenf of One Brand of Peas and the Shipment of All Others by the Minnesota Valley Canning Company in the Years 1932 and 1937.

The reason for including this chart is to illustrate an optical illusion which is seldom seen and which should be avoided. Note how the bars are distorted to the left because of the cross hatchings.

OISAIUNC INJURKS

p r