Reasoning inspector
live model stateFirm 1 price—
Firm 2 price—
Winning firm—
Firm 1 profit—
Firm 2 profit—
Current round—
Premium experiment • price undercutting between rival firms
ECONOMICS • OLIGOPOLY
Bertrand Competition, Price Wars & Nash Equilibrium
Explore Bertrand competition and price wars. Watch rival firms undercut prices, compare costs and see why price competition can drive margins toward cost.
● BERTRAND PRICE WARrival price → undercut → margin pressure
Firm 1 price
Firm 2 price
Current winner
Combined profit
Experiment with the mechanism
Bertrand competition models firms choosing prices rather than quantities. When products are close substitutes, a firm charging slightly less can capture the market, creating strong pressure to undercut any rival price that remains above marginal cost.
LEARN WITH THE SIMULATION
Understand Bertrand Competition, Price Wars & Nash Equilibrium by experimenting.
START HERE
Bertrand competition models firms that choose prices rather than quantities. When two firms sell very similar products, even a small price cut can shift customers toward the cheaper seller. That creates a strong incentive to undercut rival prices, especially when both firms still have room above marginal cost.
BUILD THE IDEA
What you should understand first
- Trace how repeated price undercutting changes market leadership and profit.
- Explain why marginal cost places a lower bound on sustainable price cutting.
- Compare Bertrand price competition with Cournot quantity competition.
TRY IT YOURSELF
What happens when one firm has a cost advantage?
- Start with similar costs and record the price path.
- Lower Firm 1 marginal cost while leaving Firm 2 unchanged.
- Replay the price rounds.
- Compare which firm can keep undercutting longer and how the final profit split changes.
Read the visual:
The lower-cost firm can sustain a lower price without pricing below cost. That gives it a strategic advantage as the price war approaches the cost floor.
WHY IT WORKS 01
Why a tiny price cut can have a large strategic effect
When products are treated as identical, buyers prefer the cheaper seller. That means a firm charging even slightly less than its rival can capture the whole market in the simplified model. If the rival price is above marginal cost, undercutting can increase profit even with only a very small price reduction. This creates repeated pressure for both firms to keep lowering price.
WHY IT WORKS 02
Why marginal cost stops the price war
A firm can only profitably undercut while the new price remains at or above its own marginal cost. Pricing below marginal cost means losing money on each additional unit sold. As both firms cut prices, that cost floor becomes increasingly important. With identical marginal costs and the classic assumptions, the Bertrand equilibrium pushes price toward marginal cost and leaves little or no economic profit.
WHY IT WORKS 03
Why Bertrand and Cournot can predict different market outcomes
Cournot firms choose quantities and recognize that total output affects market price. Bertrand firms choose prices directly and may capture customers by undercutting. Those different strategic variables change the equilibrium mechanism. With identical products and no capacity limits, Bertrand competition can be much more aggressive than Cournot competition, even with only two firms.
DO NOT MIX THESE UP
Common misconception
Bertrand competition does not mean every real market price must equal marginal cost. The classic result relies on strong assumptions such as identical products, enough capacity, customers choosing the cheaper seller, and firms setting prices simultaneously. Product differentiation and capacity limits can soften the price war.
PRACTICE CHALLENGE
Can a higher-cost firm ever win a round in the simulation?
- Give Firm 1 a lower cost than Firm 2.
- Set Firm 2's starting price below Firm 1's starting price.
- Replay several rounds.
- Explain why a temporary low price can win a round even when it is harder for the higher-cost firm to sustain that position.
Reveal the reasoning
Yes. A higher-cost firm can temporarily post the lower price and win a round, especially if it starts aggressively. But its cost floor limits how far it can keep cutting while remaining profitable. Over repeated undercutting, the lower-cost firm has more room to reduce price without selling below cost, so the cost advantage matters more as the price war develops.
MODEL BOUNDARIES
What this simulation assumes
Every simulation simplifies reality or a mathematical system. These are the assumptions and limits to keep in mind while interpreting the results.
Model assumptions
- Two firms sell highly substitutable products and compete by setting prices.
- Customers buy from the lower-price firm, with the market split on a tie.
- Firms repeatedly undercut in fixed price steps while respecting their own marginal-cost floor.
Model limitations
- Capacity limits, product differentiation, dynamic reputation and mixed strategies are omitted.
- The playback is a teaching path toward price pressure, not a general algorithm for every Bertrand equilibrium.
CONNECT IT
Where this matters
- Oligopoly pricing
- Retail price wars
- Digital markets
- Industrial organization
WORDS THAT MATTER
Key vocabulary
- Bertrand competition
- A model where rival firms compete by choosing prices.
- Undercutting
- Setting a price slightly below a rival to attract customers.
- Marginal cost
- The extra cost of producing one more unit.
- Nash equilibrium
- A set of strategies where no player wants to change strategy alone.
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