cteristics of the
relatively separate groups of wage earners in the United States to-day.
They vary greatly both in size and in kind. They are apt, however, to
be conceived as similar because of the force of logic. It is not
entirely satisfactory to classify them either as horizontal groups
(having reference to their position in the scale of skill, or of
society) or as vertical groups (having reference to their separation by
industries). For the position of certain groups may be due both to the
influence of those forces which bring about horizontal divisions, and of
those which bring about vertical divisions. Such, for example, is the
position of a craft which requires a measure of education and training
which those who are placed by circumstances at the bottom of the
industrial scale cannot easily get, and which besides it is difficult to
enter because of trade union regulations.

Marshall has described the situation in England in terms that roughly
fit the facts in the United States also. He suggests that the different
occupations may be thought of "as resembling a long flight of steps of
unequal breadth, some of them being so broad as to act as landing
stages." "Or even better still," he writes, "we may picture to ourselves
two flights of stairs, one representing the 'hard-handed industries' and
the other 'the soft-handed industries'; because the vertical division
between the two is in fact as broad and as clearly marked as the
horizontal between any two grades."[30]

The position of any relatively separate group is usually to be accounted
for only as the result of many forces, each of which has some effect
upon the rest. For example, barriers of custom or on vested right may
limit the field of employment for women. This would tend to establish
one level of earnings for women, and a different one for men. As a
result women might find it harder to get the training necessary to
enable them to compete with men. And so the interaction of causes would
proceed.

So much in the way of preliminary remark upon the characteristics of the
relatively separate groups of wage earners in the United States to-day.

3.--Among the causes which account for the existence of these groups
there are some which if they stood alone would merely modify the
applicability of the idea of a general rate of wages.

Such, for example, is the fact that the wage earner's knowledge of
existing opportunities for employment is limited. Considerab