23] See A. L. Bowley, "Distribution of Income in the United
Kingdom Before the War."

[24] Report of the Commission on the "Decline of
Agricultural Population" (Great Britain), 1906, page 14, CD
3273.

[25] H. Clay, "Economics for the General Reader," pages
237-38. See also Essay by the same author entitled, "The War
and the Status of the Wage Earner" in a volume entitled,
"The Industrial Outlook" for a more extensive analysis of
the part played by the standard of life in fixing wages.

[26] A. Marshall, "Principles of Economics" (7th edition),
page 642.

[27] Adam Smith, "Wealth of Nations" (Cannan's Ed.), Book I,
pages 101-2.

[28] F. W. Taussig, "Principles of Economics" (Revised
Edition), Vol. II, page 124.

[29] The phrase "each and all of the labor groups" is used
to indicate that the level of earnings of all the labor
groups is determined largely by forces which affect them
greatly (those examined in this chapter), and yet that the
determination of the level of earnings of each group is
something of a separate process--due to the fact that the
suppositions underlying the idea of a general rate of wages
are not fulfilled.

CHAPTER IV--PRINCIPLES OF WAGES

(_Continued_)

Section 1. We have next to examine the causes of formation of
relatively separate groups of wage earners.--Section 2. What is
meant by a "relatively separate group"?--Section 3. The causes of
the existence of these groups in the United States to-day.
Inequality of natural ability; inequality of opportunity;
artificial barriers. All these contradictory to assumptions behind
theory of general rate of wages.--Section 4. Trade unions another
factor in the formation of relatively separate groups. Indirect
effects in opposite direction.--Section 5. Each of these groups has
a relatively independent economic career. There are a series of
wage levels, all of which are governed to a considerable extent by
the same forces.--Section 6. The way in which the relative plenty
or scarcity of each kind or group of labor affects its wages. Other
forces play a part also.--Section 7. The nature of wage
"differentials."

1.--We have next, therefore, to look at the causes which lead to the
maintenance of relatively separate groups of wage earners, and then at
the forces which govern their relative levels of earnings.

2.--First of all let us make clear some of the chara