Law of Demand & Supply Concepts

Understanding the Law of Demand

  • Definition of the Law of Demand:
    • The law of demand states that there is an inverse relationship between price and the quantity demanded of a good or service.
    • When the price of a good goes up, the quantity demanded goes down.
    • When the price of a good goes down, the quantity demanded goes up.

The Importance of Assumptions in the Law of Demand

  • Key Assumption:

    • The law holds true under the assumption that quality remains constant.
    • If price increases but quality also increases, the demand may not decrease as expected.
    • Example: Higher quality may lead consumers to purchase more even at higher prices.

  • Examination Tip:

    • Students should be cautious about potential exam questions that may try to mislead them about the law of demand.
    • Always analyze the assumptions being made in any statement regarding demand.

Clarification of Concepts Related to Demand

  • Tricky Scenarios:

    • Discussed a hypothetical scenario comparing the New York Jets performance to the law of demand.
    • The statement about the Jets does not relate to the law of demand.
    • Merely having some true data does not validate or invalidate the law of demand.

  • Major Points:

    • The law of demand is concerned only with the relationship between price and the quantity demanded. Other statements, regardless of truth, do not reflect the law.

Why Quantity Demanded Changes

  • Cause of Changes:
    • The cause variable in the law of demand is the price.
    • When prices rise, purchasing power diminishes leading to decreased consumption (

Key Concepts Behind the Law of Demand:

  1. Real Income Effect:

    • As prices increase, the purchasing power of consumers decreases, leading to a decline in quantity demanded.
    • This is described as the real income effect, attributed to changes in purchasing power.
    • If prices decrease, purchasing power increases, leading to increased quantity demanded.

  2. Substitution Effect:

    • As the price of a product rises, consumers may choose to buy a substitute product instead.
    • E.g., if the price of houses increases, consumers may opt for apartments as substitutes or delay home purchases altogether.

  3. Law of Diminishing Marginal Utility:

    • This principle states that as consumers buy more of a good, the additional satisfaction (utility) derived from each additional unit tends to decrease.
    • Therefore, to encourage consumers to buy more, the price must be lowered to match the diminishing utility.
    • Example: Shoe stores may offer discounts on a second pair to incentivize purchase since the second pair offers less utility than the first.

The Demand Curve

  • Graphical Representation:

    • Typically, the price is represented on the vertical axis and the quantity demanded on the horizontal axis.
    • This results in a downward-sloping demand curve, demonstrating the negative relationship.

  • Movement vs. Shift:

    • Movement along the curve represents a change in quantity demanded due to price changes.
    • A shift of the demand curve is caused by external factors influencing demand (not price).

Examining Price Changes and Quantity Demanded

  • Scenario Example with Price:
    • If the price of a product is lowered from $50 to $40, the movement along the curve shows an increase in quantity demanded.
    • Students often mistakenly refer to moving down a curve as a decrease in quantity demanded; the curve actually moves right (increase) when quantity demanded goes up.

True/False Statements on Demand

  • Clarifying Terminology:

    • It's essential to distinguish between 'quantity demanded' (which only changes with price shifts) and 'demand' (which changes due to other factors).
    • Example: An increase in Netflix prices will decrease its quantity demanded but may increase the demand for substitute goods like Hulu.

  • Demand vs. Quantity Demanded:

    • Changing any factor other than the specific good’s price shifts demand.
    • If Netflix's price rises, but Hulu's price remains constant, we talk about changes in demand for Hulu, not quantity demanded.

Understanding Supply

  • Definition of the Law of Supply:
    • The law of supply states that there is a direct relationship between price and the quantity supplied.
    • When the price of a good increases, the quantity supplied increases.
    • When the price of a good decreases, the quantity supplied decreases.

Incentives in Supply

  • Incentives:
    • Higher prices create incentives for producers to supply more of a good because it improves profit potential.
  • Opportunity Cost:
    • Higher opportunity costs require higher prices for suppliers to cover their costs and still be willing to provide goods.

Key Concepts in Supply Analysis

  1. Change in Supply vs. Change in Quantity Supplied:

    • Change in Quantity Supplied: Occurs when the price of the good itself changes (movement along the supply curve).
    • Change in Supply: Occurs due to factors other than price (shift of the supply curve).

  2. Directional Shifts:

    • An increase in supply results in a rightward shift of the supply curve, while a decrease in supply results in a leftward shift.

Graphical Representation of Supply

  • The effective illustration for supply is likewise joined to price, with the quantity supplied moving accordingly.
  • Students should avoid confusing terminology or the interpretations of graphical movements, as these are vital for correct economic analysis.

Final Thoughts

  • Referring Back to Fundamentals:
    • It's critical for students to grasp these core differences in demand and supply to navigate complex economic discussions and problems effectively. This knowledge forms the foundation for understanding more intricate economic curves and their implications on markets.