Perfect Competition vs Monopoly vs Oligopoly
An interactive side-by-side of market and firm diagrams for the three market structures — shift demand, cost, and rivals' output to see who has a supply curve and why.
economics market structure visualization interactive October 15, 2026
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Same demand, three market structures
Shift demand or cost and watch how each structure picks its price and quantity.
Perfect competition
P = MC
S = sum of firms' MC
Flat: price taker
- P
- 5.00
- P − MC
- 0.00
Monopoly
MR = MC → P > MC
No S curve: MR = MC
Same as market
- P
- 6.92
- P − MC
- 3.08
- Q vs PC
- 3.08 vs 5.00
Oligopoly
MR = MC, given rivals
No S curve (grey = rivals, green = this firm)
D moves with rivals
- P
- 5.08
- P − MC
- 1.92
- q
- 1.92
The same comparison as a table
| Market DC | Market SC | Firm DC | Firm rule | |
|---|---|---|---|---|
| PC | Downward | Upward (sum of MCs) | Flat, | |
| Monopoly | Downward | None | market DC | |
| Oligopoly | Downward | None | Downward, but depends on rivals | , given what rivals do |
The key line: only PC has a supply curve, because only a price taker answers “price given → quantity”. The other two set , and MR depends on the demand curve — so there is no single price → quantity mapping.