The role played by agriculture in a developed urban-oriented economy such as the U.S. differs quite markedly from the heavy reliance upon agriculture which one observes in less developed nations. As an economy goes through the various stages of development, the contribution of agriculture to gross national product usually declines in relative importance. Concurrently, an increasingly complex marketing system for agricultural products develops. As transportation, trade, and other marketing services become increasingly specialized and prevalent, the interrelationships between agriculture and the rest of the economy become more numerous and increasingly complex.