Internal and external economies and diseconomies of scale

Types of Cost, Revenue and Profit

1️⃣ Cost Types

Fixed Costs (FC) are costs that do not change with the level of output (e.g., rent, salaries).

Variable Costs (VC) vary directly with output (e.g., raw materials, electricity).

Combined, total cost is: \$C = FC + VC\$

  • 📦 Example: A bakery pays £500/month for rent (FC) and £2 per loaf for flour (VC).

  • 📈 As production increases, VC rises, but FC stays the same.

2️⃣ Revenue

Revenue (R) is the total amount earned from selling goods: \$R = P \times Q\$, where \$P\$ is price and \$Q\$ is quantity sold.

📊 If a firm sells 100 units at £5 each, revenue is £500.

3️⃣ Profit

Profit (π) is revenue minus total cost: \$π = R - C\$.

💡 A positive π means the firm is making money; a negative π indicates a loss.

Short‑Run vs Long‑Run Production

Short‑Run (SR)

In the short run, at least one factor of production is fixed (usually capital).

Firms can only adjust variable inputs like labour.

  • 📉 Marginal Cost (MC) initially falls due to the law of diminishing marginal returns and then rises.

  • 📈 The SR cost curve is U‑shaped.

Long‑Run (LR)

In the long run, all inputs are variable; firms can enter or exit the market.

  • 📈 The LR cost curve is flatter than the SR curve, reflecting economies of scale.

  • 🔄 Firms can adjust plant size, technology, and workforce.

Internal & External Economies & Diseconomies of Scale

Internal Economies of Scale

These arise from within a firm as it expands:

  • 💡 Specialisation – workers focus on specific tasks, improving skill and speed.

  • 🏭 Bulk Purchasing – buying raw materials in large quantities reduces unit cost.

  • 📉 Technological Advancements – larger firms can afford automation.

External Economies of Scale

Benefits that spill over to other firms in the same industry or region:

  • 🏙️ Industry Clusters – proximity of suppliers and skilled labour reduces transport and training costs.

  • 🛠️ Shared Infrastructure – better roads, ports, and utilities lower operating costs.

Diseconomies of Scale

When a firm grows too large, costs per unit can rise:

  • 📊 Internal Diseconomies – coordination problems, communication delays, and bureaucracy.

  • 🚧 External Diseconomies – congestion, pollution, and resource depletion.

Key Equations

Average Cost (AC): \$AC = \frac{TC}{Q}\$

Marginal Cost (MC): \$MC = \frac{\Delta TC}{\Delta Q}\$

Economies of Scale (EoS) indicator: \$EoS = \frac{AC{\text{small}}}{AC{\text{large}}}\$ (EoS > 1 indicates economies of scale).

Exam Tip Box

Exam Tip: When asked to explain economies of scale, start with internal (specialisation, bulk buying) then move to external (clusters, infrastructure). For diseconomies, highlight coordination issues and external congestion.

Use the AC vs. Q diagram to illustrate how costs change as output increases.

Cost Comparison Table

Cost TypeExampleEffect on MC
Fixed CostRent, machineryDoes not affect MC directly
Variable CostRaw materials, wagesDirectly raises MC as output increases
Total CostSum of FC and VCMC is the slope of the TC curve

Quick Recap & Emoji Summary

📌 Cost Types: Fixed vs Variable

📈 Revenue: Price × Quantity

💰 Profit: Revenue – Cost

⏱️ Short‑Run: Fixed capital, variable labour

🔁 Long‑Run: All inputs variable

📉 Economies of Scale: Internal (specialisation, bulk buying) & External (clusters, infrastructure)

⚠️ Diseconomies of Scale: Coordination problems, congestion

📝 Exam Tip: Use diagrams, define key terms, and give concrete examples to illustrate each concept.