What 1890 economics book by Alfred Marshall popularized the familiar supply-and-demand diagram?

Alfred Marshall’s 1890 book Principles of Economics popularized the familiar supply-and-demand diagram.

Marshall presented demand and supply as intersecting curves whose meeting point determines an equilibrium price and quantity in a competitive market model. His graphical treatment became a standard foundation for introductory economics and helped establish modern language for market analysis.

The book also developed influential discussions of elasticity, consumer surplus, and the relationship between time periods and price adjustment. Marshall compared demand and supply to two blades of a pair of scissors, emphasizing that both help determine value.

Marshall did not invent every idea associated with the diagram. Earlier economists, including Antoine Augustin Cournot, had used mathematical and graphical approaches to demand and supply. Marshall’s achievement was to synthesize and popularize the framework for a broad economics audience.