Demand, Supply, and the Price Mechanism

Lesson Objectives and Scope

Explain Demand and Types of Demand: To articulate what constitutes demand and the various forms it takes (e.g., competitive, joint, composite, derived).
Determinants of Demand: To identify factors that influence the quantities consumers are willing to purchase.
Differentiating Demand Changes: To distinguish between a "change in demand" (a shift of the curve) and a "change in quantity demanded" (a movement along the curve).
Explain Supply and Its Determinants: To identify and explain the factors influencing producer behavior.
Differentiating Supply Changes: To distinguish between a "change in supply" and a "change in quantity supplied."
Market Equilibrium: To use diagrams and equations to explain how demand and supply establish a state of balance.
Analyzing Market Conditions: To illustrate how shifts in demand and supply affect equilibrium price ( $P$ ) and quantity ( $Q$ ).
Government Intervention: To explain the effects of subsidies, indirect taxes, and price controls (maximum and minimum prices) and examine the appropriateness of such interventions.

Meaning and Representation of Demand

Demand is defined as the various quantities of a good or service that consumers are willing and able to buy at every possible price in a given period of time. It represent a functional relationship between the price of a good and the quantity demanded of that good, ceteris paribus (all other things being equal).

This relationship can be expressed in three primary ways:

Schedule: A table showing the relationship between quantity demanded and price.
Curve: A graphical representation.
Equation: A mathematical representation.

Catherine’s Demand Schedule for Ice Cream

This table illustrates the relationship between the price of an ice-cream cone and the quantity Catherine is willing to purchase:

At a price of $\$0.00$ , the quantity demanded is $12$ cones.
At a price of $\$0.50$ , the quantity demanded is $10$ cones.
At a price of $\$1.00$ , the quantity demanded is $8$ cones.
At a price of $\$1.50$ , the quantity demanded is $6$ cones.
At a price of $\$2.00$ , the quantity demanded is $4$ cones.
At a price of $\$2.50$ , the quantity demanded is $2$ cones.
At a price of $\$3.00$ , the quantity demanded is $0$ cones.

The Demand Curve and the Law of Demand

Definition: The demand curve is a graph of the relationship between the price of a good and the quantity demanded. Plotting Catherine's schedule results in a downward-sloping curve.
The Law of Demand: Ceteris paribus, the higher the price, the lower the quantity demanded; and the lower the price, the higher the quantity demanded.
Shape: The normal demand curve is negatively sloped, indicating an inverse relationship between price and quantity.

Individual Demand vs. Market Demand

Individual Demand: The quantity demanded by a single consumer at various prices.
Market Demand: The sum of all individual demands for a particular good or service in a market.
Graphical Derivation: Individual demand curves are summed horizontally to obtain the market demand curve. It expresses the relationship between the price of a good and the total quantity demanded by all consumers.

Types of Demand

Competitive Demand: Occurs when two or more goods are substitutes for each other. Examples include margarine and butter.
Complementary (Joint) Demand: Occurs when two or more goods must be consumed together to obtain satisfaction. Examples include a car and fuel, or a cell phone and call credits.
Composite Demand: Occurs when a single good is demanded for two or more distinct uses. For example, cassava is demanded for both fufu and gari.
Derived Demand: Occurs when the demand for one good or service is the result of the demand for another good. For example, the demand for teachers or masons is derived from the demand for education or buildings.

Determinants of Demand

Multiple variables influence the buyers in a market:

Price of the Good Itself: Represented by the Law of Demand; causes movement along the curve.
Price of Related Goods: * Substitutes: Different goods serving the same purpose (e.g., Milo and Bournvita). A rise in the price of one leads to an increase in demand for the other. * Complements: Goods consumed together (e.g., petrol and cars). A rise in the price of one leads to a decrease in demand for the other.
Income of the Consumer: * Normal Goods: A rise in real income results in an increase in demand (positive relationship). * Inferior Goods: A rise in income results in a fall in demand (inverse relationship).
Taste, Preference, and Fashion: Influenced by cultural, social, and technological factors. Goods in fashion see higher demand.
Size and Structure of Population: Larger populations generally have higher demand (e.g., toothpaste demand in Nigeria vs. Ghana). A youthful population increases demand for goods patronized by youth.
Expectations (Speculation): Anticipated changes in price or supply impact current demand. For instance, a predicted rice shortage might lead families to stock up immediately.
Weather/Seasons: Demand for items like ice cream or cold water rises in extreme heat. Seasonality affects travel; airlines and hotels are booked more in summer than winter.
Advertising: Effective advertising creates awareness of quality and increases demand; poor advertising results in low demand.

Summary Table: Variables That Influence Buyers

Variable	Effect on the Demand Curve
Price	Represents a movement along the demand curve
Income	Shifts the demand curve
Prices of related goods	Shifts the demand curve
Tastes	Shifts the demand curve
Expectations	Shifts the demand curve
Number of buyers (Population)	Shifts the demand curve

Change in Quantity Demanded vs. Change in Demand

Change in Quantity Demanded

Cause: A change in the price of the good itself, while all other determinants are held constant.
Result: A movement along the existing demand curve.
Extension in Demand: A movement from a higher price to a lower price (e.g., price drops from $\$2.00$ to $\$1.00$ , quantity increases from $4$ to $8$ ).
Contraction in Demand: A movement from a lower price to a higher price (e.g., price rises from $\$1.00$ to $\$2.00$ , quantity decreases from $8$ to $4$ ).

Change in Demand

Cause: A change in any determinant of demand other than the price of the good itself (e.g., income, tastes, demographics).
Result: A bodily shift of the entire demand curve.
Increase in Demand: The curve shifts to the right (outward).
Decrease in Demand: The curve shifts to the left (inward).

Meaning and Representation of Supply

Supply is the various quantities of a product that producers are willing and able to offer for sale at various possible prices in a given period of time. Quantity supplied refers to the specific amount offered at a particular price.

Ben’s Supply Schedule for Ice Cream

At a price of $\$0.00$ , quantity supplied is $0$ .
At a price of $\$0.50$ , quantity supplied is $0$ .
At a price of $\$1.00$ , quantity supplied is $1$ .
At a price of $\$1.50$ , quantity supplied is $2$ .
At a price of $\$2.00$ , quantity supplied is $3$ .
At a price of $\$2.50$ , quantity supplied is $4$ .
At a price of $\$3.00$ , quantity supplied is $5$ .

The Law of Supply

Law: Other things being equal, the quantity supplied of a good rises when the price of the good rises.
Relationship: There is a positive (direct) relationship between price and quantity supplied.
Curve: The supply curve is a graphical representation of this relationship, usually sloping upward from left to right.

Individual Supply vs. Market Supply

Market Supply: The sum of all individual supplies from all sellers of a particular good or service. Graphically, it is the horizontal sum of individual supply curves.

Determinants of Supply

Price of the Good Itself: Higher prices increase potential profit, motivating higher supply; lower prices reduce profit and supply.
Prices of Other Goods: Firms may switch production between alternative goods. If the price of basketballs rises, a producer of footballs might switch to basketballs to increase profit, reducing the supply of footballs (substitution in production).
Cost of Production: Influenced by raw material prices and wage rates. Higher costs squeeze profit and reduce supply; lower costs increase supply.
Technology: Improvements in technology allow firms to produce more with the same inputs, increasing supply.
Indirect Taxes and Subsidies: * Indirect Taxes: Taxes on goods and services increase the unit cost of production and reduce supply. * Subsidies: Government grants to producers reduce the unit cost and increase supply.
Weather: Especially relevant in agriculture (e.g., rain-fed agriculture in Ghana). A good rainy season brings a bumper supply; drought leads to a reduction.
Expectations: Anticipating future price increases may cause producers to withhold supply currenty (e.g., fuel stations withholding fuel if they expect pump prices to rise).
Number of Sellers: Typically, the more firms in an industry, the higher the market supply.

Summary Table: Variables That Influence Sellers

Variable	Effect on the Supply Curve
Price	Represents a movement along the supply curve
Input Prices (Costs)	Shifts the supply curve
Technology	Shifts the supply curve
Expectations	Shifts the supply curve
Number of Sellers	Shifts the supply curve

Types of Supply

Complementary (Joint) Supply: When two or more goods are produced together such that a change in the supply of one changes the supply of the other (e.g., meat and hide, palm oil and palm nut).
Competitive Supply: When a good has many alternative uses (e.g., flour used for either meat pie or bread).
Composite Supply: When the total supply of a good is obtained from various sources (e.g., salt from a mine or the sea; various sources for beverages).

Market Equilibrium

Equilibrium occurs when the opposing forces of demand and supply are in a state of balance. At this point, quantity demanded ( $QD$ ) equals quantity supplied ( $QS$ ).

Equilibrium Price: The unique price that balances $QS$ and $QD$ . Graphically, it is the intersection level of the two curves.
Equilibrium Quantity: The quantity at the intersection.
Example: Based on the combined schedules, if the price is $\$2.00$ , and both demand and supply are at a quantity of $7$ , the market is in equilibrium.

Disequilibrium

Surplus (Excess Supply/Glut): Occurs when the current price is greater than the equilibrium price (P > P_E), meaning QS > QD. To clear the surplus, suppliers will lower the price.
Shortage (Excess Demand): Occurs when the price is below the equilibrium price (P < P_E), meaning QD > QS. Suppliers will raise the price as too many buyers chase too few goods.

Analyzing Changes in Market Conditions

To analyze how an event affects the market, follow these steps:

Initial State: Illustrate the equilibrium before the change.
Shift Determination: Decide if the event shifts the demand curve, the supply curve, or both.
Direction: Determine if the shift is to the right (increase) or left (decrease).
Diagram Analysis: Use the diagram to identify the new equilibrium price and quantity.
Explanation: Describe the resultant effect.

Examples of Shifts

Increase in Demand: Hot weather shifts the demand curve for ice cream to the right. This results in a higher equilibrium price and a higher equilibrium quantity.
Decrease in Supply: An increase in the price of sugar (an input) shifts the ice cream supply curve to the left. This results in a higher equilibrium price but a lower equilibrium quantity.

Government Intervention in the Price System

Governments intervene when they believe market prices are "unfair" to buyers or sellers or to correct market failures.

Means of Intervention

Providing subsidies.
Imposing indirect taxes.
Setting price controls (minimums and maximums).
Imposing regulations.

Effects of Subsidies and Indirect Taxes

Subsidies: A grant to firms. It reduces the per-unit cost of production, shifting the supply curve outward (to the right). This leads to a lower equilibrium price and higher quantity.
Indirect Taxes: Taxes on goods increase the per-unit cost of production, shifting the supply curve to the left. This results in a higher equilibrium price ( $P_t$ ) and lower equilibrium quantity ( $Q_t$ ).
Note on Relationships: * Reducing indirect taxes has the same effect as introducing a subsidy. * Removing a subsidy has the same effect as introducing an indirect tax.

Price Controls: Maximum Price (Price Ceiling)

Definition: A legal maximum price set below the equilibrium price. It is the highest legal price that can be charged.
Reasons for Imposition: To protect consumers from exploitation, control monopoly power, ensure essential goods are affordable, and control inflation.
Effects: * Shortages: QD > QS. Suppliers may hoard goods. * Queues: Allocation may shift to "first come, first served." * Black Markets: Unofficial markets may develop where goods are sold above the legal limit. * Efficiency: Forces firms to be more efficient to remain profitable.

Price Controls: Minimum Price (Price Floor)

Definition: A legal minimum price set above the equilibrium price. It is the lowest legal price that can be charged.
Examples: Minimum wage legislation, guaranteed prices for agricultural products.
Justification: Protect workers from exploitation, encourage production, and guarantee farmers a fair return.
Effects: * Surplus: QS > QD. Can lead to overproduction (e.g., the EU's CAP). * Government Burden: The government may need to spend money to buy the surplus. If they do not, market forces may eventually pull the price back down to equilibrium.

Questions & Discussion

Question regarding total tax yield: If a tax of $\$2$ on a good raises the supply curve from $S_1$ to $S_2$ , and the consumer price rises from $\$4$ to $\$5$ , while the new quantity traded is $75$ units, what is the total tax yield? Answer: Total Tax Yield = Tax per unit $\times$ Quantity = $\$2 \times 75 = \$150$ .

Concepts from Case Studies:

Uranium Mining in Australia: If mines must install expensive new equipment (increasing cost), the supply curve shifts left. If the equipment is specifically to stop environmental contamination, this is often a regulatory intervention.
Rice in Ivory Coast: Prices reached a 30-year high because demand exceeded supply. Reasons for supply decrease included bad weather, pests, disease, and under-investment. Demand increased due to a fashion for high-quality chocolate with high cocoa content.
Housing in China and Greece: In China, prices rose (leading government to discourage borrowing); in Greece, prices fell due to a decrease in income. In Greece, scientists would show this as a leftward shift of the demand curve.
Bicycles and Technology: If demand for bicycles increases (shift right) and manufacturers cut costs through new methods (supply shift right), the quantity will definitely increase, but the effect on price depends on the magnitude of the shifts.
Air Travel and Security: Increased delays at airports (a negative attribute for air travel) shift the demand for air travel to the left. This may increase demand for "substitute" travel, like cruise ships.