WAGES NOT UNIFORM — NON-COMPETING GROUPS 53 
factors. Or they may be themselves partly of international 
range; then the conditions of international trade themselves 
operate as cause, and the domestic and international factors become 
mutually dependent. 
The underlying forces are solely domestic if social or industrial 
stratification within a country rests on deep-rooted differences in 
the standards of living of its several groups. This hypothesis 
has been stated with admirable precision by Marshall : 
“Suppose that society is divided into a number of horizontal 
grades, each of which is recruited from the children of its own 
members; and each of which has its own standard of comfort, 
and increases in numbers rapidly when the earnings to be got in it 
rise above, and shrinks rapidly when they fall below that standard. 
Suppose, then, that parents can bring up their children to any 
trade in their own grade, but cannot easily raise them above it and 
will not consent to sink them below it. 
“On these suppositions the normal wage in any trade is that 
which is sufficient to enable a labourer, who has normal regularity 
of employment, to support himself and a family of normal size 
according to the standard of comfort that is normal in the grade 
to which his trade belongs; it is not dependent on demand except 
to this extent, that if there were no demand for the labour of the 
trade at that wage the trade would not exist. In other words, the 
normal wage represents the expenses of production of the labour 
according to the ruling standard of comfort.” ! 
In such case the relations of the several groups are settled by 
causes quite independent of international trade. They would 
persist if there were no such trade at all, and would be no more 
potent and no less if such trade took place on a great scale. The 
groups get their several rates of remuneration because of differ- 
ences in the conditions of supply for the several kinds of labor and 
service, not because of the quasi-fortuitous impact of demand. 
They operate as causes of price (the price of a particular kind of 
labor) ; they are not the results of the price of goods. They are 
! ** Principles of Economies,” 2d edition, pp. 557-8. I quote from the second 
edition because the statement there is more precise than in the later editions, where 
the same conception is to be found but in vaguer formulation.