Supply and Demand: Market Forces and Equilibrium

The Market Forces of Supply and Demand

Introduction to Markets and Competition

Market: Defined as a group of buyers and sellers for a particular product.
Competitive Market: Characterized by many buyers and sellers, where each individual participant has a negligible effect on the market price.
Perfectly Competitive Market: A specific type of competitive market assumed for foundational analysis, featuring:
- All goods offered are exactly the same (homogeneous).
- Buyers and sellers are so numerous that no single entity can influence the market price; each acts as a "price taker."
Assumption: For the purpose of this chapter, markets are assumed to be perfectly competitive.

Demand

Quantity Demanded ( $Q_d$ ): The amount of a good that buyers are willing and able to purchase at a specific price.
- It is represented by a single point on the demand curve.
- If the price increases, $Q_d$ will decrease.
Law of Demand: States that, ceteris paribus (other things equal), the quantity demanded of a good falls when the price of that good rises.
Demand (Curve): Represents the sum of consumers' preferences for goods or services across specific price intervals, illustrating how consumers' willingness to purchase changes as a function of various prices.

The Demand Schedule

Demand Schedule: A table that systematically shows the relationship between different prices of a good and the corresponding quantities demanded.
Example: Helen's demand for lattes
- Price of lattes ( $) | Quantity of lattes demanded ($ Q_d $)</li><li>--|--</li><li>$ 0.00 $|$ 16 $</li><li>$ 1.00 $|$ 14 $</li><li>$ 2.00 $|$ 12 $</li><li>$ 3.00 $|$ 10 $</li><li>$ 4.00 $|$ 8 $</li><li>$ 5.00 $|$ 6 $</li><li>$ 6.00 $|$ 4 $</li></ul></li><li>Helen's preferences align with the Law of Demand, showing an inverse relationship between price and quantity demanded.</li></ul><h5 id="66760fa3-66f7-4bbd-8c4a-2311731d8830" data-toc-id="66760fa3-66f7-4bbd-8c4a-2311731d8830" collapsed="false" seolevelmigrated="true">Market Demand versus Individual Demand</h5><ul><li>Market Quantity Demanded: The total sum of the quantities demanded by all buyers at each given price.</li><li>Example: Helen and Ken's combined demand for lattes (assuming they are the only buyers)<ul><li>Price ($ ) | Helen's $Qd$ | Ken's $Qd$ | Market $Q_d$
- --|--|--|--
- $0.00$ | $16$ | $8$ | $24$
- $1.00$ | $14$ | $7$ | $21$
- $2.00$ | $12$ | $6$ | $18$
- $3.00$ | $10$ | $5$ | $15$
- $4.00$ | $8$ | $4$ | $12$
- $5.00$ | $6$ | $3$ | $9$
- $6.00$ | $4$ | $2$ | $6$

Demand Curve Shifters (Non-Price Determinants of Demand)

The demand curve illustrates the relationship between price and quantity demanded, assuming all other factors are constant.
Changes in these "other things" (non-price determinants) cause the entire demand curve to shift.
Key determinants:
1. Number of Buyers (Population):
  - An increase in the number of buyers leads to an increase in the quantity demanded at every price, shifting the demand (D) curve to the right.
  - Example: If the number of buyers increases from $D1$ to $D2$, at any price like P = $3.00, demand might increase from $15$ to $20$ .
2. Income:
  - Normal Good: Demand is positively related to income.
    - An increase in income causes an increase in quantity demanded at each price, shifting the D curve to the right.
  - Inferior Good: Demand is negatively related to income.
    - An increase in income causes a decrease in quantity demanded at each price, shifting the D curve to the left.
    - Example: Public transportation might be an inferior good for some; as income rises, they might opt for cars instead.
3. Prices of Related Goods:
  - Substitutes: Two goods are substitutes if an increase in the price of one leads to an increase in the demand for the other.
    - Example: Pizza and hamburgers. If the price of pizza increases, demand for hamburgers increases, shifting the hamburger D curve to the right.
    - Other examples: Coke and Pepsi, laptops and desktop computers, compact discs and music downloads.
  - Complements: Two goods are complements if an increase in the price of one leads to a fall in demand for the other.
    - Example: Computers and software. If computer prices rise, fewer computers are bought, leading to less software demand, shifting the software D curve to the left.
    - Other examples: College tuition and textbooks, bagels and cream cheese, eggs and bacon.
4. Consumer Preferences or Tastes:
  - Anything that shifts consumer tastes toward a good will increase its demand, shifting the D curve to the right.
  - Example: The Atkins diet's popularity in the 1990s increased demand for eggs, shifting the egg D curve to the right.
5. Consumer Expectations:
  - Expectations about future prices or income influence current buying decisions.
  - Examples:
    - If people expect incomes to rise, current demand for expensive restaurant meals might increase.
    - Concerns about future job security due to a bad economy might immediately reduce demand for new automobiles.

Summary: Variables Affecting Demand

Variable | A change in this variable…
---|---
Price | …causes a movement along the D curve
Number of buyers | …shifts the D curve
Income | …shifts the D curve
Price of related goods | …shifts the D curve
Tastes | …shifts the D curve
Expectations | …shifts the D curve

Special Cases of Goods

Giffen Good:
- A rare type of inferior good where people consume more of it as its price rises, thus violating the Law of Demand.
- This occurs when cheaper, close substitutes are unavailable.
- The income effect (reduced purchasing power due to price rise forcing more consumption of the cheaper staple) dominates the substitution effect (consumers typically buy less of a good as its price rises and more of substitutes), leading to increased purchases even with higher prices.
Veblen Good (Luxury Good):
- A commodity for which consumers' preference for buying them increases as a direct function of their price.
- Higher prices confer greater status or perceived exclusivity, contrary to the Law of Demand.
- Often also a positional good.
- Examples: High-end wines, designer handbags, luxury cars. Decreasing their prices might reduce demand as they are no longer seen as exclusive or high-status.

Active Learning 1: Demand Curve for Music Downloads

Task: Draw a demand curve for music downloads and analyze its shifts.
- Scenario A: The price of iPods falls.
 - Analysis: Music downloads and iPods are complements. A fall in the price of iPods makes them more attractive, leading to increased demand for music downloads. The demand (D) curve for music downloads shifts to the right (e.g., from $D1$ to $D2$ , increasing quantity from $Q1$ to $Q2$ at price $P_1$ ).
- Scenario B: The price of music downloads falls.
 - Analysis: This is a change in the good's own price. The D curve does not shift. Instead, there is a movement along the fixed D curve to a point with a lower price (e.g., from $P1$ to $P2$ ) and a higher quantity (e.g., from $Q1$ to $Q2$ ).
- Scenario C: The price of compact discs falls.
 - Analysis: CDs and music downloads are substitutes. A fall in the price of CDs makes them more attractive, leading consumers to buy fewer music downloads. The demand (D) curve for music downloads shifts to the left (e.g., from $D1$ to $D2$ , decreasing quantity from $Q1$ to $Q2$ at price $P_1$ ).

Supply

Quantity Supplied ( $Q_s$ ): The amount of a good that sellers are willing and able to sell at a certain price.
Law of Supply: States that, ceteris paribus (other things equal), the quantity supplied of a good rises when the price of the good rises.

The Supply Schedule

Supply Schedule: A table that shows the relationship between the price of a good and the quantity supplied.
Example: Starbucks' supply of lattes
- Price of lattes ( $) | Quantity of lattes supplied ($ Q_s $)</li><li>--|--</li><li>$ 0.00 $|$ 0 $</li><li>$ 1.00 $|$ 3 $</li><li>$ 2.00 $|$ 6 $</li><li>$ 3.00 $|$ 9 $</li><li>$ 4.00 $|$ 12 $</li><li>$ 5.00 $|$ 15 $</li><li>$ 6.00 $|$ 18 $</li></ul></li><li>Starbucks' supply schedule obeys the Law of Supply, showing a positive relationship between price and quantity supplied.</li></ul><h5 id="eeed6079-fa48-4c3e-929f-2dd79992959f" data-toc-id="eeed6079-fa48-4c3e-929f-2dd79992959f" collapsed="false" seolevelmigrated="true">Market Supply versus Individual Supply</h5><ul><li>Market Quantity Supplied: The total sum of the quantities supplied by all sellers at each given price.</li><li>Example: Starbucks and Jitters' combined supply for lattes (assuming they are the only sellers)<ul><li>Price ($ ) | Starbucks $Qs$ | Jitters $Qs$ | Market $Q_s$
- --|--|--|--
- $0.00$ | $0$ | $0$ | $0$
- $1.00$ | $3$ | $2$ | $5$
- $2.00$ | $6$ | $4$ | $10$
- $3.00$ | $9$ | $6$ | $15$
- $4.00$ | $12$ | $8$ | $20$
- $5.00$ | $15$ | $10$ | $25$
- $6.00$ | $18$ | $12$ | $30$

Supply Curve Shifters (Non-Price Determinants of Supply)

The supply curve shows how price affects quantity supplied, ceteris paribus.
Changes in these "other things" (non-price determinants) cause the entire supply curve to shift.
Key determinants:
1. Input Prices: Wages, prices of raw materials, etc.
  - A fall in input prices makes production more profitable at each output price, leading firms to supply a larger quantity at each price. The supply (S) curve shifts to the right.
  - An increase in input prices makes production less profitable, shifting the S curve to the left.
  - Example: If the price of milk (an input for lattes) falls, the quantity of lattes supplied will increase at each price, shifting the S curve to the right.
2. Technology: Determines how many inputs are required to produce a unit of output.
  - A cost-saving technological improvement has the same effect as a fall in input prices: it shifts the S curve to the right (increased supply).
3. Number of Sellers (Producers):
  - An increase in the number of sellers increases the quantity supplied at each price, shifting the S curve to the right.
4. Producer Expectations:
  - Sellers may adjust their current supply based on expectations of future prices (if the good is not perishable).
  - Example: If oilfield owners expect higher oil prices in the future due to Middle East events, they might reduce current supply to save inventory and sell later at a higher price. The S curve shifts left.

Summary: Variables Affecting Supply

Variable | A change in this variable…
---|---
Price | …causes a movement along the S curve
Input prices | …shifts the S curve
Technology | …shifts the S curve
Number of sellers | …shifts the S curve
Expectations | …shifts the S curve

Active Learning 2: Supply Curve for Tax Return Preparation Software

Task: Analyze shifts in the supply curve for tax return preparation software.
- Scenario A: Retailers cut the price of the software.
 - Analysis: This is a change in the good's own price. The S curve does not shift. There is a movement down along the fixed S curve to a lower price (e.g., $P2$ ) and a lower quantity (e.g., $Q2$ ).
- Scenario B: A technological advance allows the software to be produced at lower cost.
 - Analysis: This is a change in technology, similar to a fall in input prices. It makes production more profitable. The S curve shifts to the right (e.g., from $S1$ to $S2$ ), increasing quantity supplied from $Q1$ to $Q2$ at price $P_1$ ).
- Scenario C: Professional tax return preparers raise the price of the services they provide.
 - Analysis: This affects the demand for tax preparation software (as services are a substitute), not the supply of the software itself. The S curve for the software does not shift.

Supply and Demand Together: Market Equilibrium

When the supply (S) and demand (D) curves are combined, their intersection determines the market equilibrium.
Equilibrium: The point where quantity supplied ( $Qs$ ) equals quantity demanded ( $Qd$ ).
Equilibrium Price ( $P$ ): The price at which $Qs = Qd$ (e.g., P = $3.00 in the latte market).
- P ( $) |$ Qd $|$ Qs $</li><li>--|--|--</li><li>$ 0 $|$ 24 $|$ 0 $</li><li>$ 1 $|$ 21 $|$ 5 $</li><li>$ 2 $|$ 18 $|$ 10 $</li><li>$ 3 $|$ 15 $|$ 15 $</li><li>$ 4 $|$ 12 $|$ 20 $</li><li>$ 5 $|$ 9 $|$ 25 $</li><li>$ 6 $|$ 6 $|$ 30 $</li></ul></li><li>Equilibrium Quantity ($ Q $): The quantity supplied and quantity demanded at the equilibrium price (e.g.,$ Q = 15 $lattes at$ P = $3.00 $).</li></ul><h5 id="f362d6f8-249f-4af5-891f-3967544d3fa8" data-toc-id="f362d6f8-249f-4af5-891f-3967544d3fa8" collapsed="false" seolevelmigrated="true">Market Adjustment Processes</h5><ul><li>Surplus: Occurs when quantity supplied is greater than quantity demanded ($ Qs > Qd $).<ul><li>Example: If P =$ $5.00 $, then$ Qd = 9 $lattes and$ Qs = 25 $lattes, resulting in a surplus of$ 16 $lattes ($ 25 - 9 = 16 $).</li><li>Market Response: Facing a surplus, sellers have unsold goods and try to increase sales by cutting the price.<ul><li>Price cuts cause$ Qd $to rise and$ Qs $to fall.</li><li>This process reduces the surplus.</li><li>Prices continue to fall until the market reaches equilibrium.</li></ul></li></ul></li><li>Shortage: Occurs when quantity demanded is greater than quantity supplied ($ Qd > Qs $).<ul><li>Example: If P =$ $1.00 $, then$ Qd = 21 $lattes and$ Qs = 5 $lattes, resulting in a shortage of$ 16 $lattes ($ 21 - 5 = 16 $).</li><li>Market Response: Facing a shortage, sellers realize they can sell more at a higher price and raise the price.<ul><li>Price increases cause$ Qd $to fall and$ Qs $to rise.</li><li>This process reduces the shortage.</li><li>Prices continue to rise until the market reaches equilibrium.</li></ul></li></ul></li></ul><h4 id="92dc2d47-d3d4-43f8-b7c7-c3cfa33a1699" data-toc-id="92dc2d47-d3d4-43f8-b7c7-c3cfa33a1699" collapsed="false" seolevelmigrated="true">Analyzing Changes in Equilibrium: The Three-Step Method</h4><ul><li>To determine the effects of any event on market equilibrium ($ P $and$ Q $):<ol><li>Decide whether the event shifts the S curve, the D curve, or both.</li><li>Decide the direction in which the curve(s) shift(s) (left for decrease, right for increase).</li><li>Use a supply-demand diagram to visualize how the shift changes the equilibrium price ($ P $) and quantity ($ Q).

Example 1: A Change in Demand (Increase in Price of Gas affecting Hybrid Cars)

Event to be analyzed: Increase in price of gas.
1. Curve Shift: The D curve for hybrid cars shifts because gas prices affect demand for hybrids. The S curve does not shift because gas prices do not affect the cost of producing hybrids.
2. Direction of Shift: The D curve shifts to the right ($D1$ to $D2$) because high gas prices make hybrids more attractive relative to other cars.
3. Effect on Eq'm: The shift causes an increase in both the equilibrium price (from P1 $to$ P2 $) and the equilibrium quantity (from$ Q1 $to$ Q2) of hybrid cars.
Important Distinction: When the price (P) rises, producers supply a larger quantity of hybrids. This is a movement along the existing S curve, not a shift in the S curve itself.

Terms for Shift vs. Movement Along Curve

Change in supply: A shift in the S curve, occurring when a non-price determinant of supply changes (e.g., technology, input costs).
Change in the quantity supplied: A movement along a fixed S curve, occurring only when the price (P) changes.
Change in demand: A shift in the D curve, occurring when a non-price determinant of demand changes (e.g., income, number of buyers).
Change in the quantity demanded: A movement along a fixed D curve, occurring only when the price (P) changes.

Example 2: A Change in Supply (New Technology reduces cost of producing Hybrid Cars)

Event: New technology reduces the cost of producing hybrid cars.
1. Curve Shift: The S curve shifts because the event affects the cost of production. The D curve does not shift because production technology is not a factor affecting demand.
2. Direction of Shift: The S curve shifts to the right ($S1$ to $S2$) because reduced costs make production more profitable at any given price.
3. Effect on Eq'm: The shift causes the equilibrium price to fall (from P1 $to$ P2 $) and the equilibrium quantity to rise (from$ Q1 $to$ Q2 $).</li></ol></li></ul><h5 id="61ea0b4b-c791-4643-a1e5-0d70403f91d9" data-toc-id="61ea0b4b-c791-4643-a1e5-0d70403f91d9" collapsed="false" seolevelmigrated="true">Example 3: A Change in Both Supply and Demand (Price of Gas Rises AND New Technology Reduces Production Costs)</h5><ul><li>Events: Price of gas rises and new technology reduces production costs for hybrid cars.<ol><li>Curve Shift: Both curves shift.</li><li>Direction of Shifts: The D curve shifts to the right (due to higher gas prices, increasing hybrid attractiveness). The S curve shifts to the right (due to new technology, reducing production costs).</li><li>Effect on Eq'm: The equilibrium quantity ($ Q $) unambiguously rises. However, the effect on equilibrium price ($ P $) is ambiguous:<ul><li>If demand increases more than supply,$ P $rises.</li><li>If supply increases more than demand,$ P$$ falls.

Active Learning 3: Changes in Supply and Demand for Music Downloads

Task: Use the three-step method to analyze effects on equilibrium price and quantity of music downloads.
- Event A: A fall in the price of compact discs.
  1. Curve Shift: D curve shifts (CDs are substitutes for music downloads).
  2. Direction of Shift: D shifts left (consumers buy cheaper CDs instead).
  3. Effect on Eq'm: Both equilibrium P and Q fall.
- Event B: Sellers of music downloads negotiate a reduction in the royalties they must pay for each song they sell.
  1. Curve Shift: S curve shifts (royalties are a cost of production for sellers).
  2. Direction of Shift: S shifts right (lower costs make selling more profitable).
  3. Effect on Eq'm: Equilibrium P falls, and Q rises.
- Event C: Events A and B both occur (fall in price of CDs AND fall in cost of royalties).
  1. Curve Shift: Both curves shift.
  2. Direction of Shifts: D shifts left (from Event A). S shifts right (from Event B).
  3. Effect on Eq'm: Equilibrium P unambiguously falls. The effect on equilibrium Q is ambiguous:
    - The fall in demand (left shift of D) reduces Q.
    - The increase in supply (right shift of S) increases Q.
    - The net effect on Q depends on the relative magnitudes of the shifts.

Conclusion: How Prices Allocate Resources

Core Principle: Markets are generally an effective way to organize economic activity (one of the Ten Principles of Economics).
Price Mechanism: In market economies, prices naturally adjust to balance supply and demand.
Signaling Role of Prices: These equilibrium prices serve as crucial signals that guide economic decisions for both buyers and sellers, thereby efficiently allocating scarce resources to their most valued uses.