An economic system built on the assumption that the world's supply of wealth is fixed and that nations must export more goods than they import to assure a steady supply of gold and silver into national coffers. Mercantile thinkers saw the inflow of such wealth as the key to maintaining and enhancing national power and self sufficiency. Within this context, the accumulation and development of colonies was of great importance, since colonies could supply scarce raw materials to parent nations and serve as markets for finished goods.