The U.S. economy is composed of many smaller, regional economies. Exports from the regions cause money inflows and provide a stimulus to the local economy.
Imports are a drain on local resources.
While the U.S. economy has grown remarkably over the last several years, not all regions have had the same experience. The Washington D.C. region has had a higher rate of job growth and a lower unemployment rate than the nation as a whole in the past few years. The reason for this performance has to do with the kinds of goods that it trades. The Washington area's primary industries are tourism, technology and federal contracts. The infusion of federal dollars, especially in the area of national defense, led to the development of an information technology industry in the area.