Ebrahim AlhamedFrameworks Library

m.02 · I · The Market Mechanism · Foundations of Supply & Demand

Supply, Demand & the Cost Taxonomy

Marginal cost is the supply curve. Demand is the distribution of willingness-to-pay.

A firm supplies where price meets marginal cost. The market supply curve is the aggregated marginal costs of all firms, sorted lowest to highest. The demand curve is the distribution of buyer willingness-to-pay, also sorted. Where they cross is the equilibrium — the price at which every mutually beneficial trade happens, and no more. — after Myatt

Supply meets demand.

Downward demand, upward supply, intersection at equilibrium price and quantity.

Supply and demand Supply and demand curves crossing at equilibrium — price on the vertical axis and quantity on the horizontal axis. D S equilibrium quantity price

The levers in the machine.

Cost Taxonomy · Myatt
Fixed · Variable · Marginal · Sunk
Short-run: produce if P ≥ AVC. Long-run: enter if P ≥ AC. Always supply where P = MC.
Demand Curve · Myatt
distribution of valuations · choke price · market size
Quantity demanded at price P = count of buyers with valuation ≥ P.
Perfect Competition · Classical
many small firms · homogeneous product · free entry
In equilibrium, P = MC. Consumer + producer surplus is maximised.

Looking at any new market opportunity.

  1. Sketch the supply curve. Who can supply, at what marginal cost?
  2. Sketch the demand curve. Who values this, at what price?
  3. Find the intersection. That is the price you should expect, absent market power.

Key reading · Myatt & Galeotti

Production choices in frictionless marketplaces.

The cost taxonomy — fixed, variable, marginal, sunk — is the single framework that makes all supply decisions tractable. The common management mistake is to use fixed or sunk costs to justify staying in a market where marginal cost is above price. That is always wrong.

Supply where P = MC. Ignore sunk costs.

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