Say's law

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In classical economics, Say's law, or the law of markets, is the claim that the production of a product creates demand for another product by providing something of value which can be exchanged for that other product. So, production is the source of demand. It is named after Jean-Baptiste Say. In his principal work, A Treatise on Political Economy "A product is no sooner created, than it, from that instant, affords a market for other products to the full extent of its own value." And also, "As each of us can only purchase the productions of others with his/her own productions – as the value we can buy is equal to the value we can produce, the more men can produce, the more they will purchase." Some maintain that Say further argued that this law of markets implies that a general glut (a widespread excess of supply over demand) cannot occur. If there is a surplus of one good, there must be unmet demand for another: "If certain goods remain unsold, it is because other goods are not produced...

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