Introducing Supply and Demand

Read the sections on Demand, Supply, Market Equilibrium, and Government Intervention and Disequilibrium for a mathematical exposition of the demand and supply model, clicking through to the next when you have finished each page. The chapter also covers price ceilings and price floor analysis as well as quantity regulations.

Impacts of Surpluses and Shortages on Market Equilibrium

The existence of surpluses or shortages in supply will result in disequilibrium, or a lack of balance between supply and demand levels.

Learning Objectives

Infer the outcomes of departures from equilibrium using the model of supply and demand

Key Takeaways

Key Points
  • Surpluses, or excess supply, essentially indicates that the quantity of a good or service exceeds the demand for that particular good at the price in which the producers would wish to sell ( equilibrium level).
  • In a perfectly competitive market, excess supply is equivalent to the quantity available in the market beyond the equilibrium point of intersection between supply and demand. This will result in a shift in market equilibrium towards lower price points.
  • Shortage is a term used to indicate that the supply produced is below that of the quantity being demanded by the consumers. This disparity implies that the current market equilibrium at a given price is unfit for the current supply and demand relationship.
  • In a perfectly competitive market, a shortage in supply will ultimately result in a shift in the equilibrium point, transitioning towards a higher price point due to the limited supply availability.
Key Terms
  • Disequilibrium: The loss of equilibrium or stability, especially due to an imbalance of forces.
  • surplus: That which remains when use or need is satisfied, or when a limit is reached.
  • shortage: Not enough or not sufficient for a given demand.


In the analysis of market equilibrium, specifically for pricing and volume determinations, a thorough understanding of the supply and demand inputs is critical to economics. Surpluses and shortages on the supply end can have substantial impacts on both the pricing of a specific product or service, alongside the overall quantity sold over time. Shifts such as these in the supply availability results in disequilibrium, or essentially a lack of balance between current supply and demand levels. Surpluses and shortages often result in market inefficiencies due to a shifting market equilibrium.