Market Equilibrium and Price Determination

In a competitive market, excess demand means that buyers want to purchase more than sellers are willing to supply at the prevailing price. Equilibrium price is the price at which quantity demanded equals quantity supplied. Persistent excess demand therefore creates upward pressure on price, but its effect on the eventual equilibrium depends on why the shortage persists.

How excess demand pushes prices upward

When the market price is below the equilibrium price, quantity demanded exceeds quantity supplied. Competition among buyers for the available output puts upward pressure on the market price; individual firms in a competitive market remain price takers.

• As price rises, quantity demanded falls through a movement along the demand curve, assuming other determinants of demand remain unchanged.
• The higher price increases quantity supplied through a movement along the supply curve, assuming other determinants of supply remain unchanged.
• These adjustments reduce the shortage until market clearing occurs, where quantity demanded equals quantity supplied.

When the equilibrium price itself rises

A shortage at an artificially low or temporarily prevailing price must be distinguished from a change in equilibrium. With unchanged demand and supply curves, price adjustment restores the existing equilibrium rather than creating a new one.

• An increase in demand, represented by a rightward shift of the demand curve, raises equilibrium price and quantity when the supply curve slopes upward.
• A decrease in supply, represented by a leftward shift of the supply curve, raises equilibrium price but reduces equilibrium quantity when the demand curve slopes downward.
• If demand continues to expand relative to supply, upward price pressure can recur; excess demand itself is not an equilibrium condition.

What determines the size and persistence of the price rise

The strength of the price response depends on price elasticities and the time available for adjustment. Less responsive demand or supply generally means a larger price adjustment for a given shift in the other curve.

• Agricultural supply can be relatively inelastic in the short run because production takes time, so output cannot immediately expand in response to higher prices.
• Over a longer period, producers may adjust inputs and production capacity, increasing supply and moderating upward price pressure.
• A binding price ceiling below equilibrium prevents price from clearing the market, so excess demand can persist rather than automatically producing a higher observed price.