Notes on Supply and Demand: Case Studies, Determinants, and Graphing Guidance

Key Concepts

• Topic: supply and demand, graphing, and what drives changes in price
• Core idea: price movements result from shifts in the demand or supply curve, not just movement along the same curve
• Equilibrium: intersection of demand and supply curves gives equilibrium price and quantity
• When you have a change (in determinants), you show the pre-change curves and the new equilibrium, often with a dotted line to indicate the shift
• Real-world data can reinforce concepts (leading indicators, market size, collectible value, etc.)
• Separate discussion for demand vs. supply determinants; substitutes/complements appear on the demand side, and production substitutes appear on the supply side
• The classroom emphasis: keep graphs simple and focus on explaining the why behind price changes
• Paper guidance: include the demand and supply determinants (pp. 90 for demand, pp. 97 for supply from the textbook) and insert discussion of substitutes and complements where appropriate
• Ethical/practical takeaway: data points and real-world examples strengthen arguments; there is value in linking theory to measurable indicators (e.g., building permits, registration data, etc.)
• The classroom reality: not every micro-detail needs to be graphed; focus on core concepts and the equilibrium framework

Case Studies and Illustrative Examples

• Skyline case (car example)

  • Example product: Nissan Skyline (imported from Japan)
  • Production figure: 11{,}700 units produced in 02/2002 in Japan
  • Original price in the market era: approximately P_0 \approx 50{,}000 (the instructor notes this as a $50,000 price; the paper reflects that this was considered high for a car at the time)
  • U.S. registrations: students were advised to research how many of the original 11{,}700 were registered in the United States to gauge market size in the U.S.
  • Today’s market: some Skyline models can fetch up to P_{ ext{today}} \approx 1{,}000{,}000 depending on mileage and condition; price appreciation reflects rising demand and shrinking supply over time
  • Economic interpretation: shrinking supply over time with persistent or growing demand makes the Skyline a collectible; price escalation is consistent with classic collectibles markets
  • What to reinforce in a paper: use this data point to support the idea that once supply shrinks and demand remains, price tends to rise; relate this to the demand shift or limited supply concept in the graph

• Cement/Concrete case

  • Link between demand for concrete and building activity
  • Leading indicator: number of building permits issued is a leading indicator for concrete demand (construction leads to more cement usage)
  • Graphical implication: as building permits rise, demand for cement is expected to rise (rightward shift of the demand curve), potentially driving up price if supply cannot keep pace
  • How to use in a paper: discuss how the building permit data reinforces the demand story and helps explain why price moved or would move depending on supply constraints

• Crumble cookie example (demonstrating demand and willingness to pay)

  • Price point used to illustrate perceived value: $6 cookie
  • Reasons for willingness to pay: fresh product, consistent quality, generous size, reliable daily production
  • Market implications: demonstrates how perceived value and quality affect demand; price sensitivity and consumer willingness to pay matter for demand shifts
  • Broader point: consumer preferences and perceived value are determinants of demand, influencing the position of the demand curve

• Economic snapshot: 20/80 rule (a macroeconomic framing from the talk)

  • Mentioned idea: a relatively small share of consumers (about 20%) may drive a large portion of spending, keeping a portion of the economy active while the rest operates with tighter budgets
  • Practical takeaway: in real economies, distribution of income and consumption can affect demand strength and price dynamics; consider distributional effects in analysis

Graphing Guidance and How to Show Changes

• Pre-change vs post-change visuals
  • Start with the initial demand curve D0 and supply curve S0, intersecting at equilibrium E0 = (P, Q)
  • If a determinant changes, show the shifted curve: either D1 (if demand increases) or S1 (if supply changes)
  • The new equilibrium E1 = (P', Q') is shown where the shifted curve intersects the unchanged curve (or vice versa)
  • Use a dotted line to indicate the new equilibrium price P' and quantity Q' if you’re emphasizing the shift
• Do not overcomplicate with many incremental steps
  • The assignment asks for the core shift and the resulting equilibrium; you can mention the direction (upward or downward price) and the qualitative impact (price rises, price falls, quantity changes) without plotting every minor intermediate step
• What to include in the graph for the assignment
  • Demand axis: Price (P) vertical; Quantity (Q) horizontal
  • Plot D0 and S0, mark equilibrium E0 with (P, Q)
  • Show the shift to D1 or S1 and mark the new equilibrium E1 with (P', Q')
  • Connect the idea that when demand increases (D0 → D1) with a rightward shift, price tends to rise and quantity rises; when supply decreases (S0 → S1), price tends to rise and quantity may fall depending on the magnitude of the shift
• Core graphing reminder
  • You should illustrate changes in the context of the same market (the Skyline or cement examples) to show how determinants drive shifts, not just a static price move

Demand Determinants (book reference and lecture notes)

• The instructor references six determinants of demand (as listed in the course materials, page 90):
  • Prices of related goods (substitutes and complements)
  • Expected future income
  • Number of buyers
  • Preferences/tastes
  • (Additional determinants are mentioned in the textbook; consult page 90 for the complete list)
  • (Note: In the lecture, the teacher emphasizes including these determinants in the paper and notes substitutes/complements explicitly under this section)
• How to apply these determinants in a paper
  • For each determinant, explain how it would shift the demand curve for your example good (Skyline or cement)
  • Tie each determinant to a concrete observation or data point (e.g., “if expected future income rises, more buyers may purchase a pricey collectible, shifting demand right”)
• Substitutes and complements in demand
  • Section to insert discussion on substitutes and complements under the “prices of related goods” determinant
  • Example given: if Skyline is not bought, a buyer might instead switch to a Porsche (substitute in consumption)
  • Cement example: substitute cement types or alternatives might affect demand for a specific cement brand or type

Supply Determinants (book reference and lecture notes)

• The instructor lists five determinants of supply (page 97):
  • Prices of related goods in production (substitutes in production)
  • Prices of resources and other inputs (costs of production)
  • Expected future prices
  • Number of sellers
  • Productivity (technology) improvements
• How to apply these determinants in a paper
  • Explain how each determinant would shift the supply curve for your example good
  • Use the Crumble cookie example to illustrate input costs or productivity effects (e.g., higher ingredient costs could shift supply left unless prices rise to cover costs)
• Substitutes in production (as a supply determinant)
  • If a farm or factory can switch production to a more profitable substitute, supply of the current product may decrease
• Expected future prices
  • If producers expect higher prices tomorrow, they may withhold current supply to sell more later at higher prices, shifting supply left today
• Number of sellers and productivity
  • More sellers or productivity gains shift supply right; fewer sellers or lower productivity shift supply left

Real-World Implications and Ethical/Practical Considerations

• Economic reality and distribution
  • The talk notes that a majority of people may struggle with expenses while a minority with higher income drives much of the consumption, influencing aggregate demand and economic vitality
  • This touches on macroeconomic implications, consumer welfare, and policy considerations about affordability and inflation
• Using data to support economic reasoning
  • The professor emphasizes looking up real data (e.g., car registrations, building permits) to reinforce your narrative and explain price movements
  • Incorporate data responsibly and explain how it strengthens the argument about demand or supply shifts
• Practical implications for students
  • Focus on conceptual understanding rather than overloading the graph with minute steps
  • Use the simplest graph that conveys the shift and new equilibrium, then add qualitative explanations and sources to strengthen the argument
• The broader educational point
  • Connecting theory to tangible observations (collectibles market, construction activity, consumer preferences) helps demonstrate the relevance of supply and demand in everyday markets

Equations, Formulas, and Quantitative References

• Equilibrium condition (basic):
  • Qd = Qs at the equilibrium price P^ and equilibrium quantity Q^
• Simple linear forms (illustrative; use as a teaching tool):
  • Demand: Q_d = a - bP where a > 0, b > 0
  • Supply: Q_s = c + dP where c ext{ and } d > 0
  • Solving for equilibrium: a - bP^* = c + dP^* \Rightarrow P^* = rac{a-c}{b+d}
  • Corresponding equilibrium quantity: Q^* = a - bP^* ext{ (or } Q^* = c + dP^* ext{)}
• Demand determinants (conceptual notation)
  • Let Qd = fd(P, I, P_r, E, N, T) where:
  • I = income
  • P_r = prices of related goods (substitutes and complements)
  • E = expectations about future prices/income
  • N = number of buyers
  • T = tastes/preferences
• Supply determinants (conceptual notation)
  • Let Qs = fs(P, Pr^p, R, T, E, Ns) where:
  • P_r^p = prices of related goods in production (substitutes in production)
  • R = prices of resources/inputs
  • T = productivity/technology
  • E = expected future prices
  • N_s = number of sellers
• Leading indicator concept (cement example)
  • Let D_{ ext{cement}} ext{ be a function of } B where B = number of building permits; then
  • rac{\, ext{d}D}{ ext{d}B} > 0 indicating cement demand rises with more building activity

Quick Action Items for Students

• Before the next class, pick an example you’ll analyze (Skyline or cement or another product) and sketch:
  • Pre-change demand and supply curves (D0, S0) and equilibrium (E0)
  • Identify the determinant(s) that would shift either curve and draw the shifted curve (D1 or S1)
  • Mark the new equilibrium (E1) and discuss how P* and Q* change
• For the paper, include:
  • A clear statement of the determinants you’re using and why
  • A discussion of substitutes and complements under the demand determinants
  • A discussion of production substitutes and input costs under the supply determinants
  • Supporting data (e.g., building permits, registrations, prices) to reinforce your narrative
• If unsure about graphing, ask for quick review and bring your data to class to co-plot the graph with the instructor

Summary Takeaways

• The core of supply and demand analysis is understanding how determinants shift curves and how such shifts affect equilibrium price and quantity
• Real-world examples (Skyline as a collectible, cement with building permits, Crumble cookies) illustrate how consumer preferences, production costs, and expectations drive market outcomes
• Graphs should clearly show pre-change curves and the post-change equilibrium; the rise in price often accompanies a shift in demand or a constraint on supply
• The exam expects you to identify and discuss key determinants (both demand and supply), and to connect these determinants to shifts, prices, and quantities using the equilibrium framework
• Always tie your analysis to data points or credible sources when possible to strengthen your argument