When component parts are presented in curve charts and if space will allow, it is desirable to use two charts, one showing quantities and the other showing percentages. The above charts illustrate the reason.

Chapter 37 INDEX NUMBERS SHOWN BY CURVES

in a chart showing index numbers, 100 is used as the basis of comparison. In computing index numbers, one item or the average of several consecutive items is represented as 100. All other items are expressed as percentages of the base.

Index numbers are computed and published by the U. S. Bureau of Labor Statistics, the Federal Reserve Board, the U. S. Department of Commerce, Dun and Bradstreet's, and many other statistical organizations.

REFERENCES Brown, Theodore H., Richmond F. Bingham, and V. A. Temnomeroff, Laboratory Handbook of Statistical Methods, Mc- Graw-Hill Book Company, Inc., New York, 1931

»!••» -21 11 13 14 IS •» -27 ■» •» -JO ^l -il -JJ -M-JJ 1*

Fcdrral Rctervc Bank of New York, "Monthly Review," January 1, 1937. SCALE .6

A. Index of General Production and Trade in the United States from 1919 to 1936. 1923-25 Average Equals 100%.

In index numbers, one figure is selected at 100% and all others are expressed as percentages of that figure. In this chart the average for the years from 1923 through 1925 was selected as the base figure or 100%.

1929 1930 1931 1932 1933 1934 1935 1936

Federal Reserve Bank of New York, "Monthly Review," March 1, 193 7. SCALE .7

B. Indexes of Volume of Agricultural and Non-Agricultural Exports in the United States from 1929 to 1936. 1923.25 Average Equals 100%.