The twentieth century has seen considerable economic and social changes. Among the most important is the general rise in the standard of living in the industrialised countries. The continuous growth of consumption is evidence of this ; though it is still unequally distributed across the world, this growth appears as a basic trend of unprecedented amplitude. Commerce, which is the essential link between production and consumption, has undergone profound transformation. Formally it was a passive intermediary in the service of the producer; but it has become an active economic agent with new functions that serve consumers as well as producers. Its development makes modern commerce one of the dynamic sectors of the economy.