spread to utilize them. This natural spread is limited by the cost of transportation. On the other hand, the economy of effort demands the concentration of population. Inventions and large-scale production give advantages to centralized industry. When population does not spread, we may be sure that centralized production is overcoming the disadvantage of transporting goods. If X represents the cost of moving goods and Y the advantage of centralized production, the equation that results is X < Y, that is, the effort of moving goods from place to place is less than the advantages in production and consumption that such a movement brings. Greater returns, greater population and its wider distribution go together. The one society into which we are blending will utilize the world more fully than the many local societies of the past have done, and at the same time its members will be a multitude so vast that the underpopulation of the present can be readily seen.
