Demand & Supply: Laws, Graphs, Market Equilibrium & Shifts

TAKEAWAYS:

• Demand and supply curves graphically show how price and quantity interact, with equilibrium where they intersect.
• Law of Demand: Price ↑ → Quantity Demanded ↓ (inverse relationship), while Law of Supply: Price ↑ → Quantity Supplied ↑ (direct relationship).
• Shifts in demand/supply curves (due to non-price factors) change equilibrium price and quantity, affecting markets like Kathmandu’s traffic congestion or NEPSE stock prices.
• Market equilibrium is where quantity demanded equals quantity supplied, ensuring no surplus or shortage.
• Elasticity (though covered in Unit 3) is previewed here: demand/supply responsiveness to price changes matters for firms like Daraz or Pathao in pricing strategies.
• Real-world applications include eSewa’s transaction fees (supply of digital payment services), Daraz’s discounts (demand shifts), and NTC’s call rates (supply constraints).

1. Demand: The Consumer’s Side

1.1 Definition and Law of Demand

Demand refers to the quantity of a good or service that consumers are willing and able to buy at a given price over a period. The Law of Demand states that, ceteris paribus (all else equal), there is an inverse relationship between price and quantity demanded:

• As price increases, quantity demanded decreases.
• As price decreases, quantity demanded increases.

Why?

• Substitution effect: Higher prices make substitutes more attractive (e.g., if Daraz raises prices, consumers switch to Hamrobazaar).
• Income effect: Higher prices reduce purchasing power (e.g., if NTC increases call rates, fewer people call).
• Diminishing marginal utility: The more you consume, the less additional satisfaction you get (e.g., the 5th cup of tea gives less happiness than the first).

1.2 Demand Schedule and Demand Curve

A demand schedule is a table showing the relationship between price and quantity demanded. The demand curve plots this relationship on a graph, sloping downward from left to right.

graph TD
    A["Price (₹)"] --> B["High"]
    A --> C["Low"]
    B --> D["Quantity Demanded: Low"]
    C --> E["Quantity Demanded: High"]

Example: Demand for Smartphones in Nepal (2023)

Graphical Representation:

1.3 Factors Affecting Demand (Non-Price Determinants)

Changes in these factors shift the entire demand curve (left or right), not just move along it:

Real-World Example: eSewa’s Demand Shift

• Before COVID-19: Demand for digital payments was lower (leftward curve).
• During COVID-19: Lockdowns increased online transactions → rightward shift in demand for eSewa services.

2. Supply: The Producer’s Side

2.1 Definition and Law of Supply

Supply refers to the quantity of a good or service that producers are willing and able to sell at a given price over a period. The Law of Supply states that, ceteris paribus, there is a direct relationship between price and quantity supplied:

• As price increases, quantity supplied increases.
• As price decreases, quantity supplied decreases.

Why?

• Profit incentive: Higher prices encourage firms to produce more (e.g., Daraz increases inventory if prices rise).
• Production costs: Firms can afford to produce more at higher prices (e.g., NTC supplies more data if rates increase).
• Opportunity cost: Selling a good at a higher price means forgoing other lower-profit opportunities.

2.2 Supply Schedule and Supply Curve

A supply schedule is a table showing the relationship between price and quantity supplied. The supply curve plots this relationship on a graph, sloping upward from left to right.

graph TD
    A["Price (₹)"] --> B["High"]
    A --> C["Low"]
    B --> D["Quantity Supplied: High"]
    C --> E["Quantity Supplied: Low"]

Example: Supply of Wheat in Nepal (2023)

Graphical Representation:

2.3 Factors Affecting Supply (Non-Price Determinants)

Changes in these factors shift the entire supply curve (left or right):

Real-World Example: NTC’s Supply of Internet Services

• Before 2020: Limited fiber infrastructure → leftward supply curve.
• Post-2020: Expansion of 4G/5G → rightward shift in supply, lowering prices.

3. Market Equilibrium: Where Demand Meets Supply

Market equilibrium occurs where quantity demanded equals quantity supplied. At this point:

• There is no shortage or surplus.
• The market is in balance.

3.1 Finding Equilibrium

Graphically, equilibrium is the intersection point of the demand and supply curves.

Worked Example: Kathmandu’s Traffic Congestion (Demand for Roads) Assume:

• Demand for road space: At ₹500/day, 10,000 vehicles use roads; at ₹300/day, 15,000 vehicles use roads.
• Supply of road space: At ₹500/day, 12,000 vehicles can use roads; at ₹300/day, 8,000 vehicles can use roads.

Equilibrium:

• At ₹400/day:
  • Quantity demanded = 11,000 vehicles.
  • Quantity supplied = 11,000 vehicles.
• Surplus at ₹500: 12,000 supplied vs. 10,000 demanded → congestion (traffic jams).
• Shortage at ₹300: 8,000 supplied vs. 15,000 demanded → overcrowding.

3.2 Changes in Equilibrium

When demand or supply shifts, the equilibrium price and quantity change:

Real-World Example: NEPSE Stock Prices

• 2020 COVID-19 Crash: Demand for stocks fell (pessimism) → leftward demand shift → lower prices.
• 2021 Recovery: Optimism and government policies increased supply of stocks → rightward supply shift → lower prices, higher trading volume.

4. Shifts vs. Movements Along Curves

5. Applications in Real-World Markets

5.1 eSewa: Digital Payments Demand and Supply

• Demand for eSewa:
  • Shifts right when mobile penetration increases or government promotes digital transactions.
  • Shifts left if competing apps (Khalti, IME Pay) improve.
• Supply of eSewa services:
  • Shifts right when eSewa upgrades technology (e.g., faster transactions).
  • Shifts left if regulatory costs increase.

5.2 Daraz: E-Commerce Pricing

• Demand for Daraz products:
  • Shifts right during sales events (e.g., Dashain discounts).
  • Shifts left if Hamrobazaar undercuts prices.
• Supply of Daraz inventory:
  • Shifts right when suppliers reduce costs.
  • Shifts left during supply chain disruptions (e.g., COVID-19).

5.3 NTC: Telecom Market

• Demand for mobile data:
  • Shifts right with more smartphones and remote work trends.
  • Shifts left if alternative internet options (Wi-Fi) improve.
• Supply of mobile data:
  • Shifts right with 5G rollout.
  • Shifts left if fiber costs rise.

5.4 NEPSE: Stock Market

• Demand for stocks:
  • Shifts right with economic growth expectations.
  • Shifts left during political instability.
• Supply of stocks:
  • Shifts right when companies go public.
  • Shifts left if investors sell en masse.

## In the Real World

1. eSewa’s Transaction Fees

   • Supply-side: eSewa’s cost of processing transactions (e.g., bank fees, fraud prevention) determines how much it can supply digital payments at each price.
   • Demand-side: If the government mandates digital payments (e.g., for utility bills), the demand curve for eSewa shifts right, increasing equilibrium quantity and potentially price.

2. Daraz’s Discount Strategies

   • During Dashain/Tihar, Daraz increases discounts (shifts demand curve right for its products).
   • If supply of a product (e.g., smartphones) is limited, Daraz may reduce discounts (supply curve shifts left), leading to higher prices.

3. NTC’s Call Rate Adjustments

   • If NTC invests in better infrastructure, its supply curve for mobile services shifts right, lowering call rates.
   • If demand for calls rises (e.g., during festivals), NTC may increase rates (demand curve shifts right), balancing supply and demand.

4. Kathmandu Traffic Congestion (Road Space Market)

   • Demand for roads: Increases during peak hours (shift right) or if more cars enter the market (shift right).
   • Supply of roads: Fixed in the short run → shortages occur when demand shifts right (e.g., more vehicles).
   • Solution: Increase supply (build more roads) or increase prices (toll roads) to reduce demand.

## Exam Tip

1. Graphs Are Key: Always draw demand and supply curves for numerical questions. Label:

   • Axes clearly (Price vs. Quantity).
   • Equilibrium point (E) with price (P*) and quantity (Q*).
   • Shifts (dashed lines) with explanations (e.g., "Income ↑ → Demand shifts right").

2. Ceteris Paribus: Remember, demand/supply curves assume all else is equal. If a question changes a non-price factor (e.g., "income doubles"), the entire curve shifts.

3. Shortage vs. Surplus:

   • Shortage: Quantity demanded > Quantity supplied → price rises.
   • Surplus: Quantity supplied > Quantity demanded → price falls.

4. Real-World Examples:

   • Relate to Nepali markets (eSewa, Daraz, NTC, NEPSE) in answers.
   • Use local data (e.g., "If NTC reduces data prices by 20%, supply shifts right...").

5. Common Mistakes to Avoid:

   • Movement vs. Shift: Don’t confuse changes due to price (movement) with non-price factors (shift).
   • Incorrect Labels: Always label curves as "Demand" and "Supply," not just "D" and "S."
   • Ignoring Equilibrium: Every question about price/quantity changes must end with the new equilibrium.

Practice Question: "Explain how a 20% increase in income affects the equilibrium price and quantity of organic vegetables in Nepal. Use a graph and real-world factors."

Answer Structure:

1. State the effect: Income ↑ → Demand shifts right.
2. Graph: Draw initial and new demand curve (shift right).
3. New equilibrium: Higher price (P*) and quantity (Q*).
4. Real-world factors:
   • More consumers can afford organic veggies.
   • Farmers may increase production (supply shifts right if possible).
5. Conclusion: Equilibrium price and quantity both rise.