Study Notes on Consumer and Producer Surplus
Consumer Surplus
Definition of Consumer Surplus: The happiness or welfare a consumer receives from purchasing a product for less than their willingness to pay.
Example of Consumer Surplus
Willingness to Pay (WTP) Scenario:
A consumer is willing to pay $120 for a pair of shoes but only pays $100.
Calculation of Consumer Surplus:
Consumer Surplus = Willingness to Pay - Actual Price Paid
Consumer Surplus = $120 - $100 = $20
Conclusion: The consumer gains $20 worth of extra happiness to use for other purchases.
More Examples of WTP
Second Consumer in the Store:
WTP = $130, Price = $100
Consumer Surplus = $130 - $100 = $30
Third Consumer in the Store:
WTP = $100, Price = $100
Consumer Surplus = $100 - $100 = $0
Conclusion: No extra happiness for this consumer, just breaking even.
Fourth Consumer in the Store:
WTP = $72, Price = $100
Consumer opts out from buying as they feel no surplus.
Key Principles
Willingness to Pay: Consumers do not disclose their WTP to avoid being charged that amount in the future.
Equal Importance: Economists evaluate all consumers equally when considering overall consumer surplus.
Example with Students and Textbooks
Scenario with three students:
Sergio: WTP = $200
Celine: WTP = $150
Raquel: WTP = $100
Actual price of textbook = $140.
Analysis of Purchases
Buying Decisions:
Sergio and Celine buy the textbook, Raquel does not.
Calculation of Consumer Surplus:
Sergio: Consumer Surplus = $200 - $140 = $60
Celine: Consumer Surplus = $150 - $140 = $10
Total Consumer Surplus:
Total = $60 + $10 = $70
Indicates consumer welfare in this marketplace.
Graphical Representation of Consumer Surplus
Creation of a Demand Curve:
Example uses willingness to pay (WTP) for three students to create a graph.
Price on Y-Axis, Quantity on X-Axis:
Determine quantity demanded at various price points.
As price decreases, more consumers are interested in purchasing.
Producer Surplus
Definition of Producer Surplus: The benefit producers receive from selling a product for more than their minimum acceptable price.
Example with Tutors
Scenario with three tutors:
Arturo: Minimum Acceptable Price (Willingness to Sell) = $30/hour
Monica: Willing to sell at $20/hour
Agata: Willing to sell at $10/hour
Going rate for tutoring is $25/hour.
Analysis of Tutoring Decisions
Buying decisions:
Monica and Agata will tutor at $25/hour, Arturo opts out.
Calculation of Producer Surplus:
Monica: Producer Surplus = $25 - $20 = $5
Agata: Producer Surplus = $25 - $10 = $15
Total Producer Surplus = $5 + $15 = $20
Total Surplus in a Market
Total Surplus = Consumer Surplus + Producer Surplus.
Importance of Measuring Total Surplus: Indicates overall welfare in the market.
Tax Introduction
Definition of Tax: A means for the government to collect money for services and benefits.
Excise Tax
Definition: A tax on a specific good or service (e.g., gasoline, tobacco).
Tax Effect on Market Outcomes
Introduction of a tax creates a separation between the price consumers pay and the price sellers receive.
Analysis of the Market Distortion caused by a tax:
Results in reduced quantity traded (Qt < Qstar).
Impact on Welfare Analysis
Consumer and Producer Surplus after Tax:
Consumer Surplus decreases as consumers pay more and buy less.
Producer Surplus decreases as producers get less for their goods.
Deadweight Loss
Definition: The loss of efficiency in a market dueto a tax or other distortion that prevents the market from reaching equilibrium.
Graphically represented as the area lost and not regained after the introduction of a tax.
Perfectly Inelastic Demand
Definition: Demand that does not change regardless of price, represented graphically as a vertical line on the demand curve.
Taxation Impact on Perfectly Inelastic Demand
If demand is perfectly inelastic, tax revenue can be generated without affecting quantity sold.
Example: Insulin and gas may fall under perfectly inelastic demand where quantity remains constant, leading to no deadweight loss. X