Labor mobility has likewise been important to the capacity of the American economy to adapt to changing conditions. When immigrants flooded labor markets on the East Coast, many workers moved inland, often to farmland waiting to be tilled. Similarly, economic opportunities in industrial, northern cities attracted black Americans from southern farms in the first half of the 20th century. Labor-force quality continues to be an important issue. Today, Americans consider "human capital" a key to success in numerous modern, high-technology industries. As a result, government leaders and business officials increasingly stress the importance of education and training to develop workers with the kind of nimble minds and adaptable skills needed in new industries such as computers and telecommunications. But natural resources and labor account for only part of an economic system. These resources must be organized and directed as efficiently as possible. In the American economy, managers, responding to signals from markets, perform this function. The traditional managerial structure in America is based on a top-down chain of command; authority flows from the chief executive in the boardroom, who makes sure that the entire business runs smoothly and efficiently, through various lower levels of management responsible for coordinating different parts of the enterprise, down to the foreman on the shop floor. Numerous tasks are divided among different divisions and workers. In early 20th-century America, this specialization, or division of labor, was said to reflect "scientific management" based on systematic analysis. 6