BEX5060 Chap.6 Costs, Competition and Market Power
Costs, Competition and Market Power
Firm decisions depend on the relevant cost, the time horizon and the market structure. This chapter distinguishes explicit from implicit cost, accounting from economic profit, fixed from variable cost and average from marginal reasoning. It then applies the competitive-firm rule, short-run shutdown and long-run exit before comparing perfect competition, monopoly and monopolistic competition.
The objective is not to label a company from its size, but to define the market, examine substitutes and entry barriers, and choose the correct revenue and cost comparison for the decision.
What this chapter covers
- 01
Explicit and implicit cost
- 02
Accounting and economic profit
- 03
Fixed, variable and marginal cost
- 04
Competitive firm output
- 05
Short-run shutdown and long-run exit
- 06
Monopoly and differentiated competition
Worked example · free
Separate operating, shutdown and exit decisions
- +1Accounting profit for the season is $96,000 − $74,000 − $38,000 = −$16,000, so the shed reports a loss.
- +1Revenue exceeds variable cost by $22,000. Operating contributes that amount toward the unavoidable fixed cost.
- +1If shutdown leaves the $38,000 fixed cost unchanged, shutting loses $38,000 while operating loses $16,000. Operate for the season, subject to capacity and quality constraints.
- +2In the long run, contracts and assets can become avoidable. Continue only if expected revenue covers all relevant costs and the resources earn an acceptable return compared with alternatives.
- +2Do not use the short-run contribution result as proof that the business should remain indefinitely. Re-estimate demand, cost and opportunity cost at the renewal decision.
Key terms
- Explicit cost
- A cost involving a monetary payment recorded by the business, such as wages, materials or rent.
- Implicit cost
- The opportunity cost of owner-supplied resources for which no direct payment is recorded.
- Economic profit
- Revenue minus both explicit and implicit costs, showing return above the value of the best forgone alternative.
- Marginal cost
- The increase in total cost caused by producing one additional unit of output.
- Price taker
- A firm too small relative to a competitive market to influence the market price through its own output choice.
- Barrier to entry
- A resource, legal, cost, network or strategic condition that makes entry difficult and can protect market power.
Costs, Competition and Market Power FAQ
Why can accounting profit differ from economic profit?
Accounting profit subtracts recorded expenses, while economic profit also subtracts opportunity costs such as forgone interest or owner labour. A business can report a positive accounting profit yet earn less than the resources could generate elsewhere. Economic profit therefore supports resource-allocation decisions rather than financial reporting alone.
When should a competitive firm shut down?
In the short run, shutdown is appropriate when revenue does not cover variable cost, commonly expressed as price below average variable cost. If revenue covers variable cost, production contributes toward unavoidable fixed cost even when total profit is negative. Long-run exit instead considers whether revenue covers all costs.
How do I identify market power in an agribusiness case?
Define the product and geographic market, then examine substitute products, customer switching, number of sellers or buyers, entry barriers and control over price. A large or well-known company is not automatically a monopolist. Market boundaries and alternatives determine the strength of power.
When is a fixed cost relevant to the decision?
Relevance depends on whether the cost changes between the available actions and on the decision horizon. An unavoidable lease does not change the short run output choice, but it can become avoidable at renewal and matter to exit. State the alternative and horizon first, then include incremental cash cost and opportunity cost while excluding allocations that remain under either choice.
How should I compare competitive and monopoly output decisions?
Both settings use the marginal rule, but the revenue side differs. A competitive firm takes price as marginal revenue, while a monopolist faces market demand and marginal revenue below price. Choose quantity where marginal revenue meets rising marginal cost, then read the monopoly price from demand. Keep output choice, overall profit, shutdown and welfare as separate questions.
Assessment move
Sort every number in a firm problem into incremental, avoidable, unavoidable or opportunity cost before using it. Write the decision horizon beside the table. Practise one-more-unit questions with marginal revenue and marginal cost, seasonal operating questions with revenue and variable cost, and long-run continuation questions with all relevant costs.
Build a market-structure comparison using sellers, differentiation, barriers and price control. Apply it to narrow regional input or processing markets rather than relying on brand size. Draw the competitive output rule and explain it in words. For each recommendation, add a non-financial constraint such as quality, capacity, customer effects or partner risk.
Check that allocated common cost has not been treated as avoidable unless the decision actually removes it.
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