Microeconomics: Consumer Surplus & Producer Surplus Study Notes

Microeconomics: Consumer Surplus & Producer Surplus

Welfare Economics Overview

  • Welfare economics focuses on how changes in supply and demand affect people's well-being.

  • Main points discussed:

    • Impact of market changes on consumers and producers.

    • Introduction of terminology to analyze well-being impacts.

    • Future application of concepts to analyze government interventions.

Consumer Side Analysis

  • Willingness to Pay (WTP):

    • Definition: The maximum price a consumer is willing to pay for a good or service.

    • Also referred to as reservation price.

    • Graphically represented by the height of the demand curve at a particular quantity.

  • Demand Schedule Example:

    • A demand curve illustrating WTP at different quantities.

Demand Curve Example

  • Price Points:

    • $50 for Buyer A, $40 for Buyer B, $30 for Buyer C, $20 for Buyer D, $10 for Buyer E.

  • Graph Explanation:

    • WTP is represented vertically against the quantity demanded horizontally.

Purchase Decisions

  • Attendees' willingness to buy depends on market price:

    • If the price exceeds WTP, no purchase occurs.

    • If the price is below WTP, the purchase definitely occurs.

  • At price equal to WTP, the consumer is indifferent (P = WTP).

Quantity Demanded

  • Example Scenario:

    • At a market price of $15, total quantity demanded (Qd) is 4 (four consumers have WTP >= $15).

    • Visual representation of demand shows the price corresponds with quantity demanded.

Consumer Surplus (CS)

  • Definition:

    • The net gain attained by consumers purchasing at market price lower than their WTP.

  • Calculating Individual Consumer Surplus:

    • Buyer A: WTP $50; CS = $50 - $25 (market price) = $25

    • Buyer B: WTP $40; CS = $40 - $25 = $15

    • Buyer C: WTP $30; CS = $30 - $25 = $5

    • Buyers D & E do not purchase (CS = $0).

Total Consumer Surplus

  • The sum of individual consumer surpluses (CS) results in total consumer surplus:

    • Total CS at P=$25 = $25 + $15 + $5 + $0 + $0 = $45.

  • Graphical representation: CS = area under the demand curve and above market price.

Graphical Representation of Consumer Surplus

  • Individual CS areas for buyers are highlighted in the graph according to their respective WTP and market price.

Impact of Price Changes on Consumer Surplus

  • A decrease in price has differential effects on consumers:

    • More consumers can purchase the good at lower prices.

  • Example of Price Fall: Changing price from $25 to $15 increases consumer surplus for buyers who can now purchase at the lower price.

Producer Side Analysis

  • Seller's Willingness to Sell:

    • Defined as the minimum price at which they will sell a good—also referred to as cost or seller’s reservation price.

    • The height of the supply curve indicates the marginal cost for each quantity sold.

Producer Surplus

  • Definition:

    • The difference between market price and seller's costs defines individual producer surplus.

    • Total producer surplus is the summation of all individual producer surpluses in the market.

  • Graphically, it is the area below market price and above the supply curve.

Example of Producer Surplus at Price of $25

  • Seller J: Cost $50 (does not sell)

  • Seller I: Cost $40 (does not sell)

  • Seller H: Cost $30 (does not sell)

  • Seller G: Cost $20; PS = $25 - $20 = $5

  • Seller F: Cost $10; PS = $25 - $10 = $15.

Effect of Price Change on Producer Surplus

  • Price increase from $25 to $35 leads to changes in producer surplus:

    • Existing producers benefit by higher market prices.

    • New sellers enter the market benefiting from the increased prices.

Total Surplus Definition

  • Total Surplus: The sum of consumer surplus and producer surplus.

  • Graphically illustrated as the area between the demand and supply curves up to the quantity traded.

Total Surplus Calculation

  • Example where price is $25:

    • Consumer Surplus (CS) at P=$25 calculated as:
      CS = rac{1}{2} imes (50 - 25) imes 2.5 = 31.25

    • Producer Surplus (PS) at P=$25 calculated as:
      PS = rac{1}{2} imes (25 - 10) imes 2.5 = 18.75

    • Total Surplus (TS) at price given by:
      TS = CS + PS = 31.25 + 18.75 = 50.

Market Inefficiency

  • In situations where the market is not at equilibrium (i.e., there are surpluses or shortages), trade quantities drop below equilibrium levels:

    • Excess supply (surplus) or excess demand (shortage) leads to inefficiencies.

Example of Market Distortion

  • When price exceeds equilibrium, consumers buy less than suppliers want to sell.

  • A graph illustrates the area of total surplus loss when quantities are lower due to market distortions.

Conclusion

  • Understanding consumer surplus and producer surplus aids in analyzing market efficiency and welfare economics.

  • Future emphasis may be placed on how these concepts relate to government interventions and market regulations.