Historically, the concept of income has first appeared in economics. Adam Smith, in the wealth of nations, defined income as "the amount of consumption that is not eroded by capital", and saw it as an increase in wealth. Later, most economists inherited and developed this view. 1890, ai (Alfred Marshall Maarshell) in its "the principles of economics," the Adam Smith's "wealth increase" enterprise, introduced the concept of earnings, is proposed to distinguish the entity capital and value-added benefits of economic benefits. According to the latest data released by the U.S. Department of Transportation, the number of driving miles (VMT) in October 2017 is 268 billion miles, up 0.8 percent year on year and 0.2 percent month-on-month. According to the data, total vehicle mileage is expected to reach 2.685 trillion miles in 2017.