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Supply Curve and Price Relationship

Oct 21, 2025

Overview

This lecture explains the supply curve, its relationship with price, and why it slopes upward, using oil as the key example.

The Supply Curve

  • A supply curve shows how much of a good suppliers are willing and able to sell at various prices.
  • Each good or service has its own supply curve.
  • As the price of a good increases, the quantity supplied generally increases.

Example: Oil Supply Curve

  • At $5 per barrel, 10 million barrels of oil are supplied daily.
  • At $20 per barrel, 25 million barrels are supplied daily.
  • At $55 per barrel, 50 million barrels are supplied daily.

Why the Supply Curve Slopes Upward

  • Different sources of oil have different extraction costs; cheaper sources supply first.
  • Saudi Arabia can extract oil for $2 per barrel, while extraction in Alaska can cost at least $10 per barrel.
  • Deepwater rigs like the Atlantis are the most expensive sources.
  • Higher prices make it profitable for suppliers with higher extraction costs to enter the market.
  • The supply curve slopes upward because increasing quantity requires exploiting more costly sources.

Suppliers’ Market Entry and Exit

  • Only low-cost suppliers operate when prices are low.
  • As price rises, higher-cost suppliers join the market.
  • Suppliers enter or exit the market based on profitability at current prices.

Key Terms & Definitions

  • Supply Curve — A graph showing the quantity of a good suppliers are willing to sell at different prices.
  • Quantity Supplied — The amount of a good suppliers are willing to sell at a specific price.
  • Extraction Cost — The cost to obtain a resource (like oil) from the ground.

Action Items / Next Steps

  • Review supply curve concepts and be ready for equilibrium in the next lecture.
  • Try practice questions if available.