Definition of oligopoly 寡头垄断的定义
An oligopoly is an industry dominated by a few large firms. For example, an industry with a five-firm concentration ratio of greater than 50% is considered an oligopoly. 寡头垄断是指由少数大公司主导的行业。例如，五家公司集中率超过50%的行业被认为是一个寡头垄断。
Car industry – economies of scale have caused mergers so big multinationals dominate the market. The biggest car firms include Toyota, Hyundai, Ford, General Motors, VW. 汽车行业--规模经济造成了兼并，因此大型跨国公司主导了市场。最大的汽车公司包括丰田、现代、福特、通用汽车、大众。
The UK definition of an oligopoly is a five-firm concentration ratio of more than 50% (this means the five biggest firms have more than 50% of the total market share) The above industry (UK petrol) is an example of an oligopoly. 英国对寡头垄断的定义是五家公司的集中率超过50%（这意味着五家最大的公司拥有总市场份额的50%以上）上述行业（英国汽油）是寡头垄断的一个例子。
There are different possible ways that firms in oligopoly will compete and behave this will depend upon 寡头垄断中的企业有不同的竞争方式和行为，这将取决于:
There are different possible outcomes for oligopoly 寡头垄断有不同的可能结果:
This model suggests that prices will be fairly stable and there is little incentive for firms to change prices. Therefore, firms compete using non-price competition methods. 这个模型表明，价格将相当稳定，企业改变价格的动力很小。因此，企业使用非价格竞争方法进行竞争。
The diagram above suggests that a change in marginal cost still leads to the same price, because of the kinked demand curve. Profit maximisation occurs where MR = MC at Q1. 上图表明，由于需求曲线的弯曲，边际成本的变化仍然会导致相同的价格。利润最大化发生在MR=MC的Q1。
Firms in an oligopoly may still be very competitive on price, especially if they are seeking to increase market share. In some circumstances, we can see oligopolies where firms are seeking to cut prices and increase competitiveness. 寡头垄断中的企业可能在价格上仍有很强的竞争力，尤其是在他们寻求增加市场份额的时候。在某些情况下，我们可以看到寡头垄断中的企业正在寻求削减价格，提高竞争力。
A feature of many oligopolies is selective price wars. For example, supermarkets often compete on the price of some goods (bread/special offers) but set high prices for other goods, such as luxury cake. 许多寡头垄断的一个特点是选择性的价格战。例如，超市经常在某些商品（面包/特价商品）的价格上进行竞争，但对其他商品，如豪华蛋糕，则设定高价。
In the above example, the industry was initially competitive (Qc and Pc). However, if firms collude, they can agree to restrict industry supply to Q2, and increase the price to P2. This enables the industry to become more profitable. At Qc, firms made normal profit. But, if they can stick to their quotas and keep the price at P2, they make supernormal profit. 在上述例子中，该行业最初是竞争性的（Qc和Pc）。然而，如果企业串通，他们可以同意将行业供应限制在Q2，并将价格提高到P2。这使该行业变得更加有利可图。在Qc，企业获得了正常的利润。但是，如果他们能够坚持他们的配额，并将价格保持在P2，他们就能获得超常的利润。
Game theory is looking at the decisions of firms based on the uncertainty of how other firms will react. It illustrates the concept of interdependence. For example, if a firm agrees to collude and set low output – it relies on the other firm sticking to the collusive agreement. If the firm restricts output (sets the High price), and then the other firm betrays its agreement (setting low price). The firm will be worse off. 博弈论是在其他公司将如何反应的不确定性的基础上研究公司的决定。它说明了相互依存的概念。例如，如果一家公司同意串通并设定低产出--它依赖于其他公司坚持串通协议。如果该公司限制产出（设定高价），然后其他公司背叛了协议（设定低价）。该公司的情况就会更糟。
Collusion and game theory is more complex if we add in the possibility of firms being fined by a government regulator. 如果我们加上企业被政府监管机构罚款的可能性，串通和博弈论就更加复杂。
Collusion is illegal and firms can be fined. Usually, the first firm that confesses to the regulator is protected from prosecution, so there is always an incentive to be the first to confess. 勾结是非法的，企业会被罚款。通常情况下，第一个向监管机构坦白的公司会受到保护而不被起诉，所以总是有动力成为第一个坦白的公司。
