But the complex division of labor which developed out of the
Industrial Revolution has made the exchange of products increasingly
important. To-day the typical workman concentrates upon one particular
kind of work, and is content to exchange a share of his earnings for
the numerous goods and services which he cannot supply for himself.
Exchange thus increases the total output of the community or nation by
permitting individuals to specialize in those commodities which they
can produce most effectively.

75. RELATION OF TRANSPORTATION AND COMMUNICATION TO EXCHANGE.--
Exchange is largely dependent upon transportation and communication.
In the United States, for example, not only do the individuals of a
particular community specialize in various types of work, but the
different sections of the country are devoted to the production of
those commodities for which they are best suited. Thus it is largely
true that New England is best suited to manufacturing, the South to
the growing of cotton, and certain parts of the West to the production
of lumber and foodstuffs. The suitability of a region to a particular
class of products is due, partly to location, partly to the nature of
the soil and the climate, and partly to the inclination and training
of the people. But whatever its causes, this territorial division of
labor could not be carried out without an efficient system of
transportation and communication. Communication by mail, telephone,
and telegraph is necessary to allow producers and consumers in
different parts of the country to keep in touch with one another.
Transportation by land and water is necessary if the surplus products
of one section are to be exchanged for the surplus products of other
sections.

76. TYPES OF COÖRDINATORS.--Those who perform the work of coördination