市场均衡

Market equilibrium occurs where the quantity supplied matches the quantity demanded at the same price. On a graph, this is the point where the supply and demand curves intersect. At this intersection, the equilibrium price and equilibrium quantity are determined. For example, in the sugar market, equilibrium occurs at six hundred dollars per ton with twelve million metric tons supplied and demanded.

The equilibrium price is called the market-clearing price because at this price, the market clears completely. All buyers have purchased the quantity they desire, and all sellers have sold the quantity they wish to sell. There is no surplus of unsold items or shortage of unmet demand. Everyone in the market is satisfied at this price point.

Changes in consumer preferences shift the demand curve, which alters market equilibrium. For instance, if new health research increases coffee popularity, the demand curve shifts rightward, creating a new equilibrium point with higher price and quantity. This demonstrates how external factors continuously influence the effect of shift in demand curve on market equilibrium, making equilibrium dynamic rather than static.

Production costs influence the supply curve and therefore market equilibrium. When production costs change, suppliers adjust the quantity they are willing to supply at each price level, shifting the supply curve. This shift creates a new equilibrium point with different price and quantity levels, demonstrating how supply-side factors directly impact overall market conditions.

Government regulations can shift either the supply or demand curves, altering market equilibrium. Regulations might restrict production, increase compliance costs, or change consumer behavior, all of which move the equilibrium point. These policy changes demonstrate that market equilibrium is not static but evolves with external interventions and changing market conditions.

Alfred Marshall described supply and demand as the two blades of a scissor, indicating both factors are equally important in determining equilibrium price. Just as scissors require both blades to function, markets require both supply and demand working together to establish price. Neither factor alone determines equilibrium; both must be considered simultaneously.

When quantity supplied does not equal quantity demanded, the market is not in equilibrium. If quantity supplied exceeds quantity demanded, a surplus occurs, leaving sellers with unsold items. If quantity demanded exceeds quantity supplied, a shortage occurs, leaving buyers unable to purchase desired quantities. These imbalances persist until price adjusts to restore equilibrium.