Market Equilibrium: Static vs. Dynamic, Shifts & Welfare

TAKEAWAYS:

• Market equilibrium occurs where quantity demanded equals quantity supplied (Qd = Qs), visualized by the intersection of demand and supply curves.
• Static analysis examines equilibrium at a single point in time, while dynamic analysis studies how markets adjust over time to shocks (e.g., price changes, policy shifts).
• Consumer surplus (willingness to pay minus actual price) and producer surplus (actual price minus cost) measure market efficiency and welfare.
• Shifts in demand/supply curves (due to non-price factors) cause new equilibria, altering prices and quantities (e.g., NTC’s tariff hikes or Pathao’s surge pricing).
• Short-run vs. long-run adjustments: Firms like Daraz may absorb temporary demand spikes (short-run) but adjust capacity (long-run) to restore equilibrium.
• Market failures (e.g., monopolies, externalities) reduce efficiency, requiring government intervention (e.g., NEPSE’s regulations).

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1. Market Equilibrium: The Core Concept

Market equilibrium is the balance point where the quantity buyers demand equals the quantity sellers supply at a given price. This equilibrium is stable because:

• If price > equilibrium, excess supply → downward pressure on price.
• If price < equilibrium, excess demand → upward pressure on price.

How to Find Equilibrium Mathematically

Given:

• Demand function: $Q_d=a-bP$
• Supply function: $Q_s=c+dP$

Set $Q_d=Q_s$ and solve for $P$: $$\begin{gathered} a-bP=c+dP \\ a-c=P(b+d) \\ {P}^{\ast }=\frac{a-c}{b+d} \end{gathered}$$ Substitute $P^{\ast }$ back into either equation to find $Q^{\ast }$.

Worked Example: Equilibrium in Nepal’s Mobile SIM Market

Assume:

• Demand for Ncell SIMs: $Q_d=500-10P$ (thousands/month)
• Supply by Ncell: $Q_s=100+5P$

Step 1: Find equilibrium price ($P^{\ast }$) and quantity ($Q^{\ast }$): $$\begin{gathered} 500-10P=100+5P \\ 400=15P \\ {P}^{\ast }=\frac{400}{15}\approx 26.67\text{ (Rs.)} \\ {Q}^{\ast }=500-10(26.67)=233.3\text{ (thousand SIMs)} \end{gathered}$$

Step 2: Verify with a supply-demand graph (below). At $P=26.67$, both buyers and sellers are satisfied—no excess demand or supply.

Real-World Tie-In: Ncell adjusts prices dynamically based on demand (e.g., surge pricing during festivals like Dashain). If demand spikes (e.g., 50% more users), the new equilibrium price rises, reflecting scarcity.

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2. Static vs. Dynamic Analysis: Key Differences

Dynamic Adjustment Process

When a shock hits (e.g., NTC increases internet tariffs by 20%):

1. Initial Impact: Demand for Pathao rides falls (higher costs → fewer users).
2. Short-Run Adjustment: Pathao may reduce prices to retain users, but profits drop.
3. Long-Run Adjustment: Pathao invests in cheaper tech or partnerships to restore equilibrium.

Worked Example: Daraz’s Dynamic Pricing

• Static View: At Rs. 500, 10,000 users buy a product.
• Dynamic View:
  • Day 1: Demand spikes to 15,000 (e.g., Black Friday). Daraz raises price to Rs. 600.
  • Week 2: Competitors enter. Daraz lowers price to Rs. 550 to regain market share.
  • Month 3: New equilibrium at Rs. 520, 12,000 units.

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3. Shifts in Demand and Supply: Causes and Effects

Shifts occur due to non-price factors. Use the dashed-line rule: shifts are parallel moves, while price changes are movements along the curve.

Demand Shifts (5 Key Factors)

Supply Shifts (4 Key Factors)

Worked Example: Impact of Remittance Boom on Khalti

Assume:

• Initial Equilibrium: $P=50$, $Q=100$ (million transactions/month).
• Shock: Remittances rise by 30% → demand shifts right to $Q_d=150-2P$.

New Equilibrium: $$\begin{gathered} 150-2P=50+P \\ 100=3P \\ {P}^{\ast }=33.33,Q^{\ast }=83.33 \end{gathered}$$ Result: Price falls (from Rs. 50 to Rs. 33.33) due to increased supply response (Khalti adds servers).

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4. Market Efficiency and Welfare Economics

Efficiency occurs when total surplus (consumer + producer) is maximized at equilibrium.

Consumer Surplus (CS)

• Definition: Difference between willingness to pay and actual price.
• Formula: $$CS=\frac{1}{2}\times (P_{\text{max}}-P^{\ast })\times Q^{\ast }$$
• Example: If a consumer values a Pathao ride at Rs. 100 but pays Rs. 50, $CS=50$.

Producer Surplus (PS)

• Definition: Difference between actual price and minimum acceptable price (cost).
• Formula: $$PS=\frac{1}{2}\times (P^{\ast }-P_{\text{min}})\times Q^{\ast }$$
• Example: If a Daraz seller’s cost is Rs. 200 but sells at Rs. 300, $PS=100$.

Total Surplus (TS)

$$TS=CS+PS$$ Graphical Representation:

Worked Example: Welfare in Nepal’s Rice Market

• Equilibrium: $P^{\ast }=60$, $Q^{\ast }=40$ (thousand tons).
• Max Price: Rs. 100 (consumers stop buying beyond this).
• Min Cost: Rs. 20 (farmers won’t sell below this).

Calculations: $$\begin{gathered} CS=\frac{1}{2}\times (100-60)\times 40=800\text{ (Rs. thousand)} \\ PS=\frac{1}{2}\times (60-20)\times 40=800\text{ (Rs. thousand)} \\ TS=800+800=1600\text{ (Rs. thousand)} \end{gathered}$$

Policy Impact: If the government sets a price ceiling at Rs. 40:

• New Q: 30 (shortage of 10 tons).
• CS: $\frac{1}{2}\times (100-40)\times 30=1500$ (↑).
• PS: $\frac{1}{2}\times (40-20)\times 30=300$ (↓).
• TS: 1800 (↓ due to deadweight loss).

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5. Dynamic Adjustments: Short-Run vs. Long-Run

Worked Example: NEPSE Stock Market Crash (2020)

• Short-Run: Prices fell 30% due to COVID-19 panic. Investors sold quickly.
• Long-Run: New firms entered, supply increased, and prices stabilized.

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6. Market Failures and Government Intervention

Markets fail when equilibrium is inefficient. Common failures:

1. Monopoly: Single seller (e.g., NTC) restricts output → deadweight loss.
2. Externalities: Unpriced costs/benefits (e.g., pollution from brick kilns).
3. Public Goods: Non-excludable (e.g., traffic signals in Kathmandu).
4. Asymmetric Information: Sellers know more (e.g., used cars in Daraz).

Government Solutions:

• Taxes/Subsidies: Correct externalities (e.g., tax on plastic bags).
• Price Controls: Ceilings/floors (e.g., rent control in Pokhara).
• Regulations: Break monopolies (e.g., NEPSE’s listing rules).

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In the Real World

1. Pathao’s Surge Pricing

   • Idea Used: Dynamic adjustment to excess demand.
   • How: During Dashain, demand spikes 40%. Pathao raises prices by 20% to balance supply (drivers) and demand. The new equilibrium reduces wait times and ensures drivers earn more.

2. Ncell’s Tariff Wars

   • Idea Used: Supply shifts due to competition.
   • How: When NTC lowered prices, Ncell responded by offering free data. This shifted the supply curve right (more attractive plans), forcing NTC to match or lose customers.

3. Daraz’s Warehouse Expansion

   • Idea Used: Long-run supply adjustment.
   • How: After COVID-19 demand surged, Daraz built 5 new warehouses in Nepal. This shifted the supply curve right, lowering prices and increasing equilibrium quantity by 30%.

4. Khalti’s Remittance Boom

   • Idea Used: Demand shifts from income changes.
   • How: When remittances rose 25% in 2022, Khalti’s demand curve shifted right. To meet demand, Khalti lowered transaction fees, moving along the supply curve to a new equilibrium.

5. NEPSE’s Circuit Breaker Rule

   • Idea Used: Price ceiling to prevent crashes.
   • How: During the 2020 crash, NEPSE halted trading if prices fell >10% in a day. This acted as a price floor, preventing a deeper short-run equilibrium collapse.

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Exam Tip

1. Equilibrium Questions:

   • Always set Qd = Qs and solve algebraically. Draw the graph to visualize.
   • For shifts, state the factor clearly (e.g., "income rises → demand shifts right").

2. Surplus Calculations:

   • Remember: CS = ½ × (Pmax – P) × Q**, PS = ½ × (P – Pmin) × Q*.
   • Label areas clearly in diagrams (use triangles for CS/PS).

3. Dynamic vs. Static:

   • Static: "At equilibrium, P=X, Q=Y."
   • Dynamic: Describe adjustment process (e.g., "Firms exit in short-run, but new firms enter in long-run").

4. Policy Evaluation:

   • Price Ceiling: Causes shortages if below equilibrium.
   • Price Floor: Causes surpluses if above equilibrium.
   • Always calculate deadweight loss (DWL) as the lost triangle.

5. Real-World Applications:

   • Link to Nepali examples (Ncell, Daraz, Khalti) for full marks.
   • Use current data (e.g., "Nepal’s inflation rose 8% in 2023 → demand shifted right").

Common Mistakes to Avoid:

• Forgetting to recalculate equilibrium after a shift.
• Mislabeling shifts vs. movements along curves.
• Ignoring units (e.g., Rs. vs. thousands of units).