CHAPTER IX 
SEASONAL FLUCTUATIONS 
An analysis of seasonal changes in immigration and emigration is 
desirable for two purposes, first to make possible the correction 
of the crude data for typical seasonal variation so that the cyclical 
element may be more readily analyzed; and secondly, as a basis 
for comparison with the seasonal fluctuations in employment. 
CORRECTION FOR NORMAL SEASONAL VARIATION 
Necessity. 
With few exceptions, immigration and emigration both exhibit 
pronounced seasonal fluctuations. Furthermore, when statistics 
of the total movement are separated into their constituents, the 
several elements are found to exhibit different typical seasonal 
movements. To illustrate, the typical seasonal for the ‘no occu- 
pation’ group is essentially different from that for the groups for 
which the designated occupations are “laborer” or ‘farm laborer.” 
In all groups, however, the seasonal is sufficiently pronounced to 
make direct analysis of the original data difficult. To facilitate 
study of the susceptibility of the migratory currents to cyclical 
fluctuations in employment, it is necessary, as we have noted in 
previous chapters, to determine the typical seasonal movement 
and by abstracting this typical seasonal fluctuation from the original 
data, to leave a residue which represents the best available estimate 
of the influence of the remaining elements—trend, cycle, and 
accidental factors. 
In most instances, it has been found desirable to eliminate also 
the influence of the trend, leaving ‘“‘cycles’”’ which represent the 
influence of cyclical and ““accidental’’ factors alone. 
Period. 
An examination of graphs of the various immigrant and emigrant 
series reveals the fact that prior to the middle of 1914 most of them 
evidence a reasonably consistent seasonal movement, but that in 
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