II. Supply and Demand Dynamics
- Supply and Demand Dynamics
The Law of Demand and Its Determinants
- Law of Demand: This law states there is an inverse relationship between price and quantity demanded. As price rises, quantity demanded decreases; as price falls, quantity demanded increases.
- Demand vs. Quantity Demanded: A change in price affects the quantity demanded (a movement along the demand curve). A change in a determinant of demand affects demand itself (a shift of the entire curve).
- Downward Sloping Curve: The demand curve slopes downward due to the law of demand and the principle of diminishing marginal utility, which states that the satisfaction gained from consuming each additional unit of a good decreases.
- Determinants of Demand: These six factors shift the demand curve:
| Determinant | Description | Impact on Demand Curve |
| Taste or Preference | Changes in consumer preferences for a good. | Shifts right for increased preference, left for decreased preference. |
| Income | Changes in consumer income. Affects normal goods (demand increases with income) and inferior goods (demand decreases with income). | Shifts right for normal goods with higher income; left for inferior goods. |
| Substitution Effect | Consumers switch to a cheaper alternative if the price of a desired good becomes too high. | Shifts left if a substitute’s price falls; right if it rises. |
| Price of Complements | Change in the price of goods used together (e.g., hot dogs and buns). | Shifts left if a complement’s price rises; right if it falls. |
| Population | An increase or decrease in the number of consumers. | Shifts right with population growth, left with decline. |
| Consumer Expectations | Anticipation of future price changes. | Shifts right if a future price increase is expected; left if a future price drop is expected. |
The Law of Supply and Its Determinants
- Law of Supply: This law states there is a positive relationship between price and quantity supplied. As price rises, the quantity supplied increases; as price falls, quantity supplied decreases.
- Supply vs. Quantity Supplied: A change in price affects the quantity supplied (a movement along the supply curve). A change in a determinant affects supply (a shift of the entire curve).
- Determinants of Supply: These six factors shift the supply curve:
| Determinant | Description | Impact on Supply Curve |
| Input Prices | Changes in the cost of resources (land, labor, capital) used in production. | Shifts left if input prices rise; right if they fall. |
| Producers’ Expectations | Anticipation of future events, such as changes in raw material prices. | Shifts right if producers expect future shortages and increase current production. |
| Technology | Technological advancements improve efficiency and lower production costs. | Shifts right. |
| Price of Other Goods | A change in the price of another good a supplier could produce. | Shifts left for good A if the price of good B rises, incentivizing production of B. |
| Number of Suppliers | More suppliers entering the market increases overall supply. | Shifts right as suppliers increase, left as they decrease. |
| Government Action | Changes in taxes (increase costs) or subsidies (decrease costs). | Shifts left with higher taxes; right with subsidies. |
Market Equilibrium, Price Controls, and Elasticity
- Equilibrium: In a market, the intersection of the supply and demand curves determines the equilibrium price and equilibrium quantity. At this point, the amount consumers are willing to buy equals the amount suppliers are willing to sell.
- Surplus and Shortage: A price above equilibrium results in a surplus (quantity supplied > quantity demanded). A price below equilibrium results in a shortage (quantity demanded > quantity supplied).
- Price Controls:
- Price Ceiling: A government-mandated maximum price (e.g., rent control). To be effective, it must be set below the equilibrium price, which creates a shortage.
- Price Floor: A government-mandated minimum price (e.g., minimum wage). To be effective, it must be set above the equilibrium price, which creates a surplus.
- Elasticity: This concept measures the responsiveness of quantity demanded or supplied to a change in one of its determinants.
- Price Elasticity of Demand: Measures how much quantity demanded responds to a price change. If the result of the calculation is > 1, demand is elastic (responsive). If < 1, it is inelastic (unresponsive). If = 1, it is unitary elastic. Determinants include the availability of substitutes, the good’s importance relative to budget, and the time period.
- Price Elasticity of Supply: Measures how much quantity supplied responds to a price change. The main determinant is the amount of time a producer has to respond to a price change.
- Cross-Elasticity of Demand: Measures how the quantity demanded of one good responds to a price change in another. A positive result indicates substitute goods; a negative result indicates complementary goods.
- Income Elasticity of Demand: Measures how quantity demanded responds to a change in income. A positive result indicates a normal good; a negative result indicates an inferior good.