📚 Firms’ Costs, Revenue and Objectives | 企业的成本、收益与目标
In economics, a firm is any business organisation that combines factors of production to produce goods and services. To make rational decisions, firms must understand their costs and revenue, and they must decide what objective to pursue. Costs determine the supply side, revenue determines the demand side from the firm’s viewpoint, and objectives determine how the firm balances them.
在经济学中，企业是指组合生产要素以生产商品和服务的任何商业组织。为了做出理性决策，企业必须了解自己的成本与收益，并决定追求的目标。成本决定了供给方面，从企业角度看收益决定了需求方面，而目标决定了企业如何权衡二者。
1. The Firm and Its Core Objectives | 企业与核心目标
In traditional economic theory, the core objective of a firm is profit maximisation. Profit is the difference between total revenue and total cost, so managers must consider both sides of the account. However, not all firms aim solely at profit; some may pursue growth, market share, survival, or social goals, especially in the real world.
在传统经济理论中，企业的核心目标是利润最大化。利润是总收益与总成本之差，因此管理者必须同时考虑收支两面。然而，并非所有企业都以利润为唯一目标；有些企业可能追求增长、市场份额、生存或社会目标，尤其在现实世界中。
In the Cambridge IGCSE syllabus, you are expected to know how costs and revenue affect profit and how different objectives influence the firm’s pricing and output decisions.
在剑桥 IGCSE 教学大纲中，考生需要了解成本与收益如何影响利润，以及不同目标如何影响企业的定价和产量决策。
2. Fixed Costs and Variable Costs | 固定成本与可变成本
Costs can be classified by how they respond to changes in output. Fixed costs do not change when output changes; they are incurred even if the firm produces nothing. Variable costs change directly as output changes.
成本可按其对产量变化的反应进行分类。固定成本不随产量变化而变化；即使企业不生产也会发生。可变成本则随产量变化而直接变化。
- Examples of fixed costs include rent, insurance, and salaries of permanent managers. 固定成本的例子包括租金、保险费和固定管理人员的工资。
- Examples of variable costs include raw materials, energy used in production, and hourly wages for temporary workers. 可变成本的例子包括原材料、生产用电以及临时工的计时工资。
In the short run, some costs are fixed, but in the long run all costs become variable.
在短期内，部分成本是固定的；但在长期中，所有成本都可变。
3. Total, Average and Marginal Cost | 总成本、平均成本与边际成本
Total cost (TC) is the full cost of producing a given quantity of output. Average cost (AC) is the cost per unit, calculated as TC divided by output. Marginal cost (MC) is the extra cost of producing one more unit.
总成本（TC）是生产一定产量所需要的全部成本。平均成本（AC）是每单位产品的成本，等于总成本除以产量。边际成本（MC）是多生产一单位产品所增加的成本。
AC = TC/Q | MC = ΔTC/ΔQ
Initially, as output rises, both AC and MC may fall because of increasing efficiency. Later, diminishing returns cause MC to rise, and when MC rises above AC, AC starts to increase. Thus both curves are U-shaped.
起初，随着产量增加，由于效率提高，AC 和 MC 都可能下降。之后，边际报酬递减使 MC 上升；当 MC 高于 AC 时，AC 开始上升。因此两条曲线均为 U 形。
4. Short-run Production and the Law of Diminishing Returns | 短期生产与边际报酬递减
In the short run, at least one factor of production is fixed, such as capital. When a firm adds more variable factors (e.g. labour) to a fixed factor, the marginal product of labour first rises and then falls. This is the law of diminishing returns.
在短期内，至少有一种生产要素是固定的，例如资本。当企业在固定要素上不断增加可变要素（如劳动力）时，劳动力的边际产量先上升后下降。这就是边际报酬递减规律。
Because marginal cost is the inverse of marginal product, MC first falls and then rises. This explains the rising part of the MC curve and the eventual rise in average cost.
由于边际成本是边际产量的倒数，MC 先下降后上升。这解释了 MC 曲线的上升部分以及平均成本最终上升的原因。
5. Long-run Costs: Economies and Diseconomies of Scale | 长期成本与规模经济/规模不经济
In the long run, all factors are variable, so the firm can change the scale of production. As the scale of production increases, the long-run average cost (LRAC) may fall due to economies of scale; eventually it may rise due to diseconomies of scale.
在长期中，所有要素均可变，因此企业可以改变生产规模。随着生产规模扩大，长期平均成本（LRAC）可能因规模经济而下降；最终也可能因规模不经济而上升。
Sources of economies of scale include:
规模经济的来源包括：
- Technical: large machines and specialised labour are more efficient. 技术：大型机器和专业化劳动力更有效率。
- Managerial: specialised managers reduce inefficiency. 管理：专业化管理减少低效率。
- Financial: larger firms can borrow at lower interest rates. 金融：规模更大的企业能以更低利率借款。
- Marketing and purchasing: bulk buying and cheaper advertising per unit. 营销与采购：批量购买和单位广告成本降低。
Diseconomies of scale arise from difficult co-ordination and poor communication in large organisations, raising LRAC.
规模不经济源于大型组织内协调困难和沟通不畅，使 LRAC 上升。
6. Total, Average and Marginal Revenue | 总收益、平均收益与边际收益
Total revenue (TR) is the firm’s total earnings from selling output, equal to price multiplied by quantity. Average revenue (AR) is revenue per unit, equal to price. Marginal revenue (MR) is the extra revenue gained from selling one more unit.
总收益（TR）是企业通过销售产品获得的总收入，等于价格乘以数量。平均收益（AR）是每单位产品的收益，等于价格。边际收益（MR）是多销售一单位产品所增加的收益。
TR = P × Q | AR = TR/Q = P | MR = ΔTR/ΔQ
In a perfectly competitive market, a firm is a price taker, so AR and MR are constant and equal to price. In an imperfectly competitive market, the firm faces a downward-sloping demand curve, so MR is less than AR and falls as output increases.
在完全竞争市场中，企业是价格接受者，因此 AR 和 MR 保持不变且等于价格。在不完全竞争市场中，企业面临向右下方倾斜的需求曲线，因此 MR 小于 AR，并随产量增加而下降。
7. Profit Maximisation as the Main Aim | 利润最大化作为主要目标
Profit is the difference between total revenue and total cost. The firm aims to produce the quantity where the gap between TR and TC is greatest, which is the same condition as setting marginal revenue equal to marginal cost.
利润是总收益与总成本之差。企业的目标是在 TR 和 TC 之间的差距最大时生产，这与令边际收益等于边际成本的条件相同。
Profit = TR − TC | Profit maximised when MR = MC
If MR > MC, increasing output adds more to revenue than to cost, so profit rises. If MR < MC, producing less would reduce cost more than revenue, so profit rises by lowering output. Hence profit is maximised only at MR = MC.
如果 MR > MC，增加产量所增加的收入大于成本，因此利润上升；如果 MR < MC，减少产量所能减少的成本大于收入，因此降低产量会使利润上升。因此，只有在 MR = MC 时利润最大化。
8. Alternative Objectives: Revenue and Sales Maximisation | 其他目标：收益最大化与销售最大化
Some firms do not maximise profit but instead maximise total revenue. Revenue is maximised when MR = 0, because selling one more unit would not change total revenue. This point is usually at a lower price and higher output than the profit-maximising point.
有些企业不是最大化利润，而是最大化总收益。收益最大化发生在 MR = 0 时，因为再多卖一单位不会改变总收益。这一点通常比利润最大化点价格更低、产量更高。
Sales maximisation, as described by William Baumol, means maximising the volume of sales (total revenue) subject to a minimum profit constraint. Managers often pursue this because salaries and status may be linked to sales size.
威廉·鲍莫尔所描述的销售最大化，是指在满足最低利润约束下最大化销售量（总收益）。管理者常追求这一目标，因为薪酬和地位可能与销售规模挂钩。
For IGCSE, you should be able to compare profit maximisation with revenue maximisation and sales maximisation on a cost–revenue diagram.
在 IGCSE 考试中，你应该能在成本–收益图中比较利润最大化、收益最大化与销售最大化。
9. Survival, Growth and Social Objectives | 生存、增长与社会目标
In some circumstances, firms may have a primary objective of survival, especially during recessions or when a new firm enters a competitive market. Growth is another objective, often achieved through mergers or investment. Growth may be pursued to increase market power or to gain economies of scale.
在某些情况下，企业可能将生存作为首要目标，尤其是在经济衰退或新企业进入竞争市场时。增长是另一个目标，通常通过合并或投资实现；企业追求增长可能是为了增强市场势力或获得规模经济。
Some firms also adopt social objectives, such as environmental protection or fair trade, in line with corporate social responsibility (CSR). Public corporations may aim to protect consumers or ensure a stable supply.
一些企业也采纳社会目标，如环境保护或公平贸易，以符合企业社会责任（CSR）。公有制企业可能以保护消费者或确保稳定供应为目标。
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