The market Forces of Supply and Demand Supply and demand are the two words that economists use most often Supply and demand are the forces that make market economies work Modern microeconomics is about supply, demand, and market equilibrium. Harcourt, Inc. items and derived items copyright o 200l by harcourt, IncHarcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. The Market Forces of Supply and Demand Supply and demand are the two words that economists use most often. Supply and demand are the forces that make market economies work. Modern microeconomics is about supply, demand, and market equilibrium