ABSTRACT
People may work longer hours, or a larger proportion of the population may enter the labor force, or a larger proportion of incomes may be saved and used to accumulate more capital. Moreover, some of the most interesting and subtle aspects of the process of economic change concern the interrelationships among the various sources of such change, the dependence of the behavior of one variable upon the simultaneous behavior of one or more other variables. The productivity-increasing impact of technological change has had major effects on the structure and organization of our modern economic system. Technological indivisibilities which dictate very large producing units far in excess of local requirements, heavy reliance upon the utilization of fossil fuels as energy sources, regional specialization of a highly productive agricultural sector: these factors create a powerful trend toward geographic concentration.
