OPPORTUNITIES FOR IMMIGRANTS 5 
the concensus of opinion of commentators on employment con- 
ditions that this class bears the chief brunt of cyclical and seasonal 
variations in employment, and furthermore, it is the immigrant 
who makes up a large part of the unskilled labor group. 
For much of our analysis, monthly, or at least quarterly, rather 
than annual data are essential. Annual data serve well to give 
indications of general tendencies, but the picture which may be 
drawn with them is necessarily only in broad outline and permits 
symptomatic details to be obscured. For example, with only 
annual data, it becomes impossible to determine, with any reason- 
able degree of precision, whether the immigrant tide slackens in 
premonition of an impending industrial slump, or, on the contrary, 
begins to ebb only after employment has been on the decline for 
several months. 
Lastly, if we could have an equally comprehensive index of 
fluctuations of economic opportunities in the country from which 
immigrants come, we should feel excellently equipped for the task 
before us. 
The data actually available do not make possible the construction 
of such an ideal index as that just outlined, but, nevertheless, 
afford, in our judgment, a basis for reasonably accurate conclusions, 
particularly when reinforced by other indices of industrial activity. 
Types of Employment Statistics. 
The principal sources of information concerning employment 
conditions in the United States are of four types: (1) indirect 
evidences of employment conditions as found in statistics of production 
and such even less direct indices of employment opportunities 
as are afforded by prices, clearings, and other indicators of business 
activity; (2) records of the average number of wage earners employed 
during the month, or the number employed on a given day, as 
shown by payroll data; (3) statistics of the percentage of trade union 
members unemployed; and (4) employment office statistics, giving the 
ratio of applicants to jobs. All four of these types have been 
utilized in the subsequent analysis, although the primary index of 
factory employment by months, for the period beginning with 
1889, has been constructed from statistics of the average number 
employed, supplemented for a portion of the period by trade union 
statistics of unemployment. 
LA