Individuals receive most of their income as suppliers of the factors of production As laborers they receive wages. As landlords they receive rent As lenders of money capital they receive interest. As owners or part owners of business firms they receive an income that is partly interest and partly pro fits. We have seen above that their decisions in disposing of thisincomedetermine what goods will be produced and in what quantities.
　　In primitive times, individuals and families satisfied their own wants directly by hunting and fishing and gathering wild foods. If they had clothing, it was the skins of animals they had killed themselves They built their own shelter in the form of huts or of tents made from skins. Later some people started to raise agricultural products and others started to breed
domesticated animals for their own use As long as these conditions persisted, the economy was simple to understand and explain Later, however, we began to have some specialization and division of labor. Some skilled individuals began to devote most of their time to making bows and arrows and trading them to the hunters for meat. Some people discovered how to make clay pots and traded them to others for agricultural products. In some places people discovered how to weave cloth and traded the cloth for other products. Most primitive tribes developed some form of money to overcome the difficulties of direct barter exchange.
　　Our present economic system represents an extremely high development of this principle of specialization and division of labor. Few people now produce goods for their own use and almost no one produces all the different kinds of goods that he wishes to use. Instead we find large numbers of individuals who devote all their working time to making a small part of
one particular article or performing one particular operation in a productive process. Others are performing various kinds of specialized services, most people sell their productive services for money and then use the money to buy goods and services that are produced by a large number of other people. Some people are engaged in making machines that will be used
to make other machines or tools with which to manufacture goods.
　　This process of specialization and division of labor results in a tremendously greater output of goods and services than would be possible without it. It also makes us extremely
dependent upon other people both to buy the goods or services that we help to produce and to supply the goods or services for us to buy that we do not produce for ourselves. This interdependence contributes to the complexity and severity of many problems arising out of changes in economic activity. In spite of the problems created by interdependence, almost no
one advocates a return to a system of individual family self-sufficiency. Not only would a return to self-sufficiency mean a greatly reduced standard of living; it is doudtful if the present population could even be maintained under such a system
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　　凡是为生产提供要素的人都获得自己的大部分收入。当工人的，他们领取工资。做房地产主的，他们就收取租金。作为货币资本的贷款儿他们就获得利息。在企业公司中作财东或股东的，他们获得的收入中一部分是股息，一部分是利润。由此可见，这些人怎样处理这类收入，决定着以后生产商品的晶种与数量。
　　在远古时代，个人和家庭直接靠打猎、捕鱼、采集野果来满足本身的需要。他们要穿衣服，就穿自己猎杀的野兽的皮。他们用兽皮为自己搭盖帐棚形状的栖身之处。后来，就有些人开始种植农作物，还有些人开始饲养家畜，供自己食用。处于这种状态的时期，经济社会单纯，容易理解，也容易阐明。
但是，后来我们开始产生了某些专业化和劳动分工。一些手巧的人开始用自己的大部分时间专心制造弓箭，用来向猎人换取肉类。有些人发明了制造陶器的方法，并用来换取别人的农产品。有些地方的人发明了织布的方法，于是就用布换取其它产品。大多数原始部落都出现了某种形式的货币，以克服以物易物进行直接交换所带来的种种困难。
　　我们当今的经济体制体现了专业化和劳动分工这一原则的高度发展。现在很少有人为自己使用而生产商品，简直没有人能够生产出他所要使用的各种商品。恰恰相反，我们所见到的都是大批大批的人花费他们的全部工作时间都为某一种特定产品制造一种小零件，或是在一道工序中负责一项特定操作。其他人则从事各种各样的专业化服务工作。大部分人都出卖自己的生产性劳务来赚取货币，然后用这些货币去购买众人所捉供的商品和劳务。有些人以制造机器为业，而这些机器又要用来制造生产商品的其他机器或工具。
　　采用了专业化和劳动分工的步骤，必然导致商品和劳务的极大规模增产，远非往日可比。这一步骤也使我们非依赖于他人不可——这些人既购买我们参与生产的商品或劳务，又补充我们自己不生产的商品和劳务供我们购买。这种依存关系助长了由于经济活动变迁而产生的许多问题的复杂性和严重性。尽管这种依存关系带来了许多问题，但是可能没有人主张复辟自给自足的个体家庭体制。向自给自足制开倒车不仅意味着生活水平的大退化，甚至现有人口能否在这样一种体制下生存下去都很难说。