Marginalism

Marginalism Overview

/

Definition of Marginalism

  • Marginalism is a concept in economics that emphasizes decision-making at the edge or margin of a process rather than on average outcomes. It specifically focuses on the incremental changes associated with a decision.

    • Key Questions:

    • What is the additional output from one more unit of input?

    • What are the costs and revenues associated with producing one more unit?

    • This approach underscores the importance of analyses that consider small increments to optimize decision-making related to resources.

Core Concept: Marginal Product

  • Marginal Product (MP): The additional output gained from using one more unit of an input.

    • Inputs can include:

    • One more worker

    • One more hour of irrigation

    • One more bag of seed

    • One more acre of land

    • Example of Hiring Farm Workers:
      | Workers (Total) | Total Harvest (Bushels) | Marginal Product (Bushels) |
      |------------------|--------------------------|-----------------------------|
      | 0 | 0 | - |
      | 1 | 10 | 10 |
      | 2 | 25 | 15 |
      | 3 | 35 | 10 |
      | 4 | 40 | 5 |
      | 5 | 42 | 2 |

    • Observation: The marginal product eventually falls, illustrating the Law of Diminishing Marginal Returns.

Visualization of Product Curves

  • Curves Representations:

    • Total Product (TP): Overall output from all units used.

    • Marginal Product (MP): The additional output resulting from the use of one more unit.

    • Diminishing Returns: Describes the decrease in marginal product when increasing an input factor beyond a certain point.

Cost and Revenue at the Margin

  • Each economic decision involves weighing the costs and benefits.

    • Marginal Cost (MC): The additional cost incurred by producing one more unit of output.

    • Example: The cost of fuel and seed to produce one more bushel of wheat.

    • Marginal Revenue (MR): The additional revenue obtained from selling one more unit of output.

    • For a farmer in a large market, the MR is typically the market price.

The Optimal Decision Rule

  • A rational farmer should continue an activity as long as the marginal benefit is greater than or equal to the marginal cost.

    • Profit-Maximizing Rule:

    • Produce until MR = MC.

    • Decision Outcomes:

    • If MR > MC: Produce one more unit to increase profit.

    • If MR < MC: Do not produce that unit as it decreases profit.

    • If MR = MC: Stop production - profit is maximized.

Visualizing the Profit Maximizing Point

  • The intersection of the Marginal Revenue (MR) and Marginal Cost (MC) curves indicates the optimal quantity to produce.

    • Price and Quantity Illustration:

    • Quantity (Q)

    • Price, Cost

      • Marginal Cost (MC)

      • Marginal Revenue (MR)

    • Zones Identified:

      • Profitable Zone (MR > MC)

      • Loss Zone (MC > MR)

Application: The Fertilizer Decision

  • Decision Inquiry: How many bags of fertilizer should a farmer apply?

    • Cost of One Bag of Fertilizer (MC) = $25

    • Price of One Bushel of Corn (P) = $5

    • Process: The farmer calculates the value of the marginal product based on incremental fertilizer applications.

    • Tabulated Decisions:
      | Bags of Fertilizer | Marginal Prod. (Extra Bushels) | Marginal Rev. ($) | Marginal Cost ($) | Decision |
      |-------------------|--------------------------------|--------------------|---------------------|----------------------|
      | 1st bag | 8 | $40 | $25 | Apply |
      | 2nd bag | 7 | $35 | $25 | Apply |
      | 3rd bag | 5 | $25 | $25 | Apply |
      | 4th bag | 3 | $15 | $25 | Stop |
      | 5th bag | 1 | $5 | $25 | Stop |

    • The optimal decision is to stop after applying 3 bags, where marginal revenue equals marginal cost.

Another Example: Pesticide Application

  • Question: How many times should a farmer spray a soybean field for pests?

    • Cost of One Pesticide Application (MC) = $150

    • Price of One Bushel of Soybeans (P) = $12

    • Analysis Process: Similar to the fertilizer decision, the farmer compares marginal revenue to marginal cost for each spray.

    • Tabulated Decisions:
      | Pesticide Application | Marginal Product (Bushels Saved) | Marginal Rev. ($) | Marginal Cost ($) | Decision |
      |-----------------------|----------------------------------|--------------------|---------------------|----------------------|
      | 1st spray | 20 | $240 | $150 | Apply |
      | 2nd spray | 15 | $180 | $150 | Apply |
      | 3rd spray | 13 | $156 | $150 | Apply |
      | 4th spray | 10 | $120 | $150 | Stop |
      | 5th spray | 5 | $60 | $150 | Stop |

    • The optimal decision is also to stop after 3 applications, as the cost exceeds the revenue generated from the fourth spray.

Revenue and Pricing Relationships

  • Total Revenue (TR) can be defined and illustrated using the area of the rectangle formed by price and quantity.

    • Formulas:

    • Total Revenue = Price (P) × Quantity (Q)

    • Marginal Revenue typically equals market price in competitive markets (MR = P).

Concepts of Cost Structures

  • Understanding the relationships among Price, Marginal Cost (MC), and Average Total Cost (ATC).

  • Key principles include:

    • Intersection points of MR and MC help in identifying the optimal production quantity (Q*).

    • The geometric representation of costs, revenues, and the profit maximization framework could help in making informed production decisions.