解題
Part (a) Solution:
1. Define the Objectives:
- Profit maximisation occurs at the output level where Marginal Cost equals Marginal Revenue (\(MC = MR\)), and the MC curve cuts the MR curve from below.
- Revenue maximisation occurs at the output level where Marginal Revenue is zero (\(MR = 0\)). At this point, the price elasticity of demand is unitary (\(PED = 1\)).
2. Analytical Comparison:
- Output: Because the MR curve is downward-sloping, the point where \(MR = 0\) (revenue max) will always lie to the right of the point where \(MC = MR\) (profit max, assuming positive MC). Therefore, output will increase (from \(Q_{pm}\) to \(Q_{rm}\)).
- Price: Since the firm faces a downward-sloping demand curve (Average Revenue, \(AR\)), an increase in output requires a reduction in price. Thus, price will fall (from \(P_{pm}\) to \(P_{rm}\)).
- Profits: Total profit is maximised at \(Q_{pm}\). Any expansion of output beyond this point means that \(MC > MR\) for those extra units, which reduces total profit. Therefore, total profit will decrease, and the firm may even make a loss if the revenue-maximising price falls below Average Total Cost (\(ATC\)).
3. Diagrammatic Analysis:
- The candidate should draw a standard imperfectly competitive firm diagram with downward-sloping \(AR\) and \(MR\) curves, and U-shaped \(ATC\) and \(MC\) curves.
- Clearly label \(Q_{pm}\) and \(P_{pm}\) where \(MC = MR\).
- Clearly label \(Q_{rm}\) and \(P_{rm}\) where \(MR = 0\) (projected up to the \(AR\) curve).
- Show that \(Q_{rm} > Q_{pm}\) and \(P_{rm} < P_{pm}\), with the profit area being smaller at \(Q_{rm}\).
Part (b) Solution:
1. Introduction:
- Briefly outline imperfectly competitive markets (monopoly, oligopoly, monopolistic competition) and identify alternative objectives that firms might pursue, such as sales maximisation (\(AC = AR\)), growth, satisficing, or Corporate Social Responsibility (CSR).
2. Arguments supporting the view (Why firms must return to profit maximisation in the long run):
- Shareholder Pressure and Principal-Agent Problem: In the long run, divorce of ownership and control can lead to conflict. Shareholders demand dividends and capital growth. If managers continuously sacrifice profits for other goals, shareholders may replace management or launch a hostile takeover.
- Survival and Finance: In the long run, firms need retained profits to finance research and development (R&D) and product innovation (dynamic efficiency). This is crucial in imperfectly competitive markets to maintain market share against competitors.
- Opportunity Cost of Capital: If profits remain below the normal rate, capital will eventually exit the industry to seek higher returns elsewhere.
3. Arguments challenging the view (Why firms do not always return to profit maximisation):
- Barriers to Entry and Monopoly Power: If barriers to entry are high, a firm can make substantial supernormal profits even when pursuing other objectives (like satisficing). It does not face the same survival pressures as competitive firms.
- Enlightened Self-Interest / Strategic CSR: Pursuing ethical or environmental goals can enhance brand reputation, increase consumer loyalty, and reduce long-term costs (e.g., avoiding government regulation). In this sense, non-profit objectives in the short/medium term can actually support long-term profit maximisation.
- State Intervention or Public Interest: Some imperfectly competitive firms may be state-owned or heavily regulated, meaning their primary long-run mandate is allocative efficiency or social welfare rather than profit.
4. Evaluation and Conclusion:
- A good essay will offer a reasoned conclusion. While firms have the discretion to pursue non-maximising objectives in the short run due to separation of ownership and control, profit maximisation remains the ultimate constraint in the long run for most private sector firms. Without a minimum ('satisficing') level of profit, survival is threatened, but the 'always' in the prompt is too strong because highly secure monopolies or socially integrated firms can sustain alternative objectives indefinitely.
評分準則
Part (a) [8 marks total]:
- Up to 4 marks: Accurate diagram showing AR, MR, MC, and ATC curves. Clear identification of profit-maximising output/price (where MC=MR) and revenue-maximising output/price (where MR=0).
- Up to 4 marks: Explanation of the transition. Clarifying that output rises because MR is positive up to the revenue-maximising point, price falls to clear the market of the higher output, and profit falls because the firm produces where MC > MR.
Part (b) [12 marks total]:
- Level 3 (9-12 marks): Balanced and analytical evaluation of both sides. Evaluates the long-run pressures of shareholders, takeovers, and need for R&D (forcing profit maximisation) against countervailing factors like market power, long-run brand value of CSR, and satisficing behavior. Offers a clear, reasoned conclusion.
- Level 2 (5-8 marks): Good explanation of alternative objectives and some discussion of long-run viability. Explains why profit maximisation is important but lacks deep evaluation or a balanced view.
- Level 1 (1-4 marks): Identifies alternative objectives with limited or no evaluation. Mostly descriptive text about firms' goals.