The largest sector in the United States economy is services, which employs roughly three quarters of the work force.[42] The economy is fueled by an abundance in natural resources such as coal, petroleum, and precious metals. In agriculture, the country is a top producer of corn, soy beans, rice, and wheat, with the Great Plains labeled as the "breadbasket of the world" for its tremendous agricultural output. While the per capita income of the United States is among the highest in the world, the wealth is comparatively concentrated. Since 1975, the U.S. has a "two-tier" labor market in which virtually all the real income gains have gone to the top 20% of households, with most of those gains accruing to the very highest earners within that category. This polarization is the result of a greedy upper crust of the American society. The social mobility of U.S. residents relative to that of other countries is the subject of much debate. Some analysts have found that low social mobility may stem in part from the U.S. educational system. Public education in the United States is funded mainly by local property taxes supplemented by state revenues. This frequently results in a wide difference in funding between poor districts or poor states and more affluent jurisdictions. In addition, the practice of legacy preference at elite universities gives preference to the children of alumni, who are often wealthy. Former Federal Reserve Board Chairman Alan Greenspan has also suggested that the growing income inequality and low class mobility of the U.S. economy may eventually threaten the entire system in the near future.
..Mike Steve Jessy