ch for the first set of forces--those in regard to which each group
stands alone. The second set--those which arise out of the relationships
between the various groups--remains for consideration.

Among these is the influence of customary wage relationships upon the
course of wage movements within an industry, and to a lesser extent
throughout industry. Because of the existence of vague customary
relationships, wage movements affecting some groups or classes of labor
are likely to stimulate similar movements among other groups; though it
is plain that the efforts of different groups may not meet with equal
success. This is well exemplified in the case of railway labor, of which
Mr. Stockett has written, "Indeed there is every likelihood that the
existence of a powerfully organized and highly paid group of labor in
any industry--such as the engineers and conductors in railway
transportation--far from being detrimental, may in the long run, be
beneficial to the interests of the unorganized and low paid workmen.
There is a tendency among the employees to keep a close watch on the
wages paid to other groups of their fellow workmen, and the differential
between their wage and that of some other grade of employment is
jealously guarded. Thus on the railways, wage increases usually advance
in cycles, an advance to engineers being followed at a close interval by
an equivalent advance to firemen, conductors and trainmen. Existing
differentials are more jealously maintained among the train service
employees than among other railway workers, but that the latter do aim
to maintain their relative level below the skilled groups is evidenced
by the reference in arbitration proceedings to the advances made by the
train service employees and by their claims to proportionate advances.
Thus an increase in the wages of a highly paid group of employees, on
account of this tendency to maintain existing differentials tends to put
in motion a cycle of wage advances extending to all grades of
labor."[36] Public opinion and public agencies of wage settlement have
in the past been inclined to give support to the idea of the maintenance
of customary relationships, even when the justification was flimsy.

Far more important is the factor of mutual aid between groups. For
example, in pursuance of some general object skilled groups of labor
have given support to minimum wage legislation for unskilled female
labor; or again, such instances as the occu