In addition to food shortages， rapid population growth will increase the pollution of the environment.
Some economists argue that the boom in services is caused mainly by firms contracting out jobs they used to do for themselves， such as catering， advertising and data-processing.
Services are the fastest-growing part of international trade，accounting for 20% of total world trade and 30% of American exports.
Labor in the United States possesses a high skill level and works with large amounts of capital equipment. These factors contribute to the high productivity and the high hourly wages of American workers.
Most people hold some of their wealth in the form of money because it provides readily available purchasing power for dealing with an uncertain future
During a time of inflation， the purchasing power of money will decline， imposing a cost on those who are holding wealth in the form of money.
To limit the market of an industry to one country would often mean reduced efficiency and higher costs.
International trade enables a country to obtain products that cannot be produced at home at all or that cannot be produced in adequate quantities and at acceptable costs.
The Industrial Revolution was characterized by specialization of individuals in their work tasks.
7.06% of the total population of Shanghai have a bachelor‘s degree， making the educational level of the city well ahead of the national average of graduates per head of population which currently stands at 1.59%.