INFLUENCE OF ECONOMIC CONDITIONS 171
States, Great Britain, and Germany.: Professor Hansen divides his
series into three groups: the Investment, Industrial, and Banking
Groups, respectively. Of these, the Industrial Group is most pertinent
 to a study of migration. For the United States the Industrial
Group is constituted of wholesale commodity prices, pig iron
production, railroad gross earnings, imports, and immigration; for
Germany, of wholesale prices and pig iron production; and for
Great Britain, of imports and exports.
After careful analysis of these three composites, Professor Hansen
comes to the conclusion that ‘“‘the cyclical movements are quite
closely concurrent,” that is, there is a general tendency for the
periods of prosperity to coincide in these countries and likewise for
the depression troughs to be reached about the same time.
Our own analysis of comparative economic conditions in this
and other countries is based chiefly upon certain statistical indices
of economic activities, to be described presently, and upon portions
of descriptive annals of industrial and agricultural conditions prepared
 by Dr. Willard Thorp, of the research staff of the National
Bureau of Economic Research.
Composite Indices of Economic Activity.
To facilitate the international comparison of business cycles,
we have utilized composite indices of economic activity in the respective
 countries. For the United States we made use of a composite
 index prepared by Professor W. F. Ogburn and Dorothy S.
Thomas, for the years from 1870 to 1920, using nine economic series:
namely, wholesale prices (1870-1915), commercial failures (1870-1920),
 bituminous coal production (1870-1920), pig iron production
(1870-1920), railroad freight ton mileage (1882-1920), bank clearings
outside New York City (1881-1915), employment in Massachusetts
(1889-1920), railroad mileage constructed (1870-1888), and imports
(1870-1888). In constructing this index a mathematical trend
curve was fitted to each series, the percentage deviations therefrom
computed, and the results expressed as cycles, in units of the typical
or standard deviation. Then the cycles thus obtained for each
separate series were averaged to obtain the composite index.
For the United Kingdom, Germany, and Italy, we have com-3Alvin
 Harvey Hansen, Cycles of Prosperity and Depression in the United States,
Great Britain and Germany—A study of Monthly Data 1902-1908, University of Wisconsin
 Studies in the Social Sciences and History, Number 5.
“The Influence of the Business Cycle on Certain Social Conditions,” Quarterly
Publication of the American Statistical Association, September, 1922, p. 327.