Why Cartels Are Unstable: Individual vs. Joint Profit

Collective monopoly profit conflicts with individual gain.

Check Three Incentive Comparisons

The economic comparisons below use stated demand, costs and available actions. A group’s preferred outcome need not be an equilibrium of individual choices. In the United States, naked agreements among competitors to fix prices or restrict output are unlawful; this lesson analyzes hypothetical incentives, rather than recommending conduct for businesses.

Separate Individual and Joint Profit

The standard cartel model compares joint profit maximization with each member’s incentive to deviate. Extra output can increase one member’s profit while its rival holds output fixed, even though the market price falls. Whether the change is profitable depends on demand and costs; the label “cartel” does not replace that calculation.

Check the Output and Cost Assumptions

In a smooth interior joint-profit model, compare industry MR with the marginal cost of producing total output efficiently across firms. With different firm costs, the allocation of that output matters. A unilateral expansion generally changes the market price on all units sold; do not calculate profit by holding the old price fixed without justification.

Compare Unilateral and Mutual Expansion

In the usual downward-sloping-demand example, expansion by both firms raises total output and reduces price. A profitable unilateral deviation can therefore coexist with lower joint profit. An equilibrium requires checking each firm’s available deviations, rather than assuming that a jointly preferred outcome will be individually chosen.

Treat Coordination Factors as Evidence

Market conditions affect the risk of coordination. Observability, rivals’ likely responses and aligned incentives are relevant evidence, not guarantees. Hidden discounts and uncertain demand can make conduct harder to interpret. Legal consequences also matter; a hypothetical payoff model should not be mistaken for a legal permission to coordinate.

Check the Repeated-Game Assumptions

In a repeated-game model, a current gain can be offset by a change in future payoffs. The conclusion depends on the horizon, information, future weighting and whether the specified responses are credible within the model. Repetition alone does not remove a current incentive or guarantee cooperation. If the problem states a known final period, examine that period’s incentives instead of assuming indefinite future consequences.

Examine Entry and Cost Differences

Feasible entry by independent outsiders can constrain incumbent pricing; a potential entrant is not automatically an effective rival. Differing production costs can also create disagreement over output allocations. Product similarity can make prices easier to compare, while differences in service or contract terms can complicate comparisons. Use the conditions actually supplied in the problem.

Recompute Changed Payoffs

Game questions sometimes ask what happens after a payoff changes. Recompute best responses rather than carrying the old equilibrium forward. A subsidy to one strategy, a penalty for collusion, or a change in future profit can remove a dominant strategy or create a different Nash equilibrium. The labels “cooperate” and “defect” do not determine the answer. The displayed payoffs do.

Calculate the 40-Unit Quota Example

Make the original 40-unit quota story explicit. Suppose market demand is P = 240 − Q, where Q = qA + qB, and each firm’s total cost is 80 times its own output, with no fixed cost. At 40 units each, total output is 80, price is $160 and each profit is ($160 − $80) × 40 = $3,200. If only A expands by 10 units, price falls to $150: A earns $3,500 and B earns $2,800. If both expand to 50, price is $140 and each earns $3,000. These invented assumptions support the comparison; extra sales alone would not have proved it.

Distinguish Agreement from Parallel Pricing

Similar prices or simultaneous price changes can result from independent responses to the same market conditions. A price-fixing agreement need not be written: it can be verbal or inferred from conduct and other evidence. Neither identical prices alone nor the absence of a signed document settles whether an agreement exists. An economics problem should be answered from its stated facts; do not infer a real legal outcome from a simple diagram.

Separate Joint Profit and Total Surplus

Under the standard model with downward-sloping demand, the same production technology and no externalities or other distortions, joint monopoly-like restriction creates underproduction relative to the competitive benchmark. Higher joint producer profit is different from higher total surplus. State those assumptions rather than treating every collaboration between firms as economically identical.

Explain the Specific Incentive

When asked about cartel instability, identify a supported deviation incentive or a stated entry mechanism. The existence of an incentive does not prove the exact timing of collapse. A useful answer names whose payoff changes, holds the rival’s action fixed for that comparison and then checks the outcome when both respond.

Check the Incentive and Agreement Definitions

OpenStax’s oligopoly lesson introduces the conflict between joint profit and unilateral incentives. The FTC’s price-fixing guidance distinguishes agreements from independent price responses and explains that an agreement need not be written. The DOJ’s coordination discussion describes conditional market evidence. The new numerical model and questions here are original classroom examples.

Read an Original Two-Choice Payoff Matrix

For this simplified one-period game only, each firm must choose either 40 or 50 units. Use the demand and cost assumptions above. Each cell lists Firm A’s profit first and Firm B’s second, in dollars. The matrix restricts the available actions; it does not claim that 50 is optimal when every possible output is allowed.

Try Three Cartel-Incentive Questions

Connect Incentives, Concentration and Output

Review what concentration measures can establish, connect output choice with price and profit, and continue in the CLEP Microeconomics learning hub.