R12 练习: 企业与市场结构
考纲范围
- determine and interpret breakeven and shutdown points of production under perfect and imperfect competition.
- determine and interpret how economies and diseconomies of scale affect costs under perfect and imperfect competition.
- describe characteristics of perfect competition, monopolistic competition, oligopoly, and pure monopoly.
- explain supply and demand relationships under monopolistic competition, including the optimal price and output for firms as well as pricing strategy.
- explain supply and demand relationships under oligopoly, including the optimal price and output for firms as well as pricing strategy.
- identify the type of market structure within which a firm operates and describe the use and limitations of concentration measures.
Q1.
In the long run, which of the following statements is most accurate for a survived firm in a perfectly competitive market?
Statement 1: The firm will produce goods at the lowest average cost.
Statement 2: The firm may earn zero economic profit.
A. Statement 1
B. Statement 2
C. Both of statement 1 and statement 2
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答案：C
解析：在完全竞争市场的长期均衡中，存活的企业在LRATC的最低点生产（Statement 1正确），且经济利润为零（Statement 2正确，用”may”表述也是准确的）。长期均衡时 P = MC = LRATC最低点。
选项 判断 解析 A ✗ 仅Statement 1正确是不完整的，Statement 2也正确 B ✗ 仅Statement 2正确是不完整的，Statement 1也正确 C ✓ 两个陈述在长期完全竞争均衡中都是正确的 关联：R12: 企业与市场结构
Q2.
In a monopolistic market, which of the following conditions must hold for a firm to maximize profit?
A. Price equals marginal cost.
B. Marginal revenue equals marginal cost.
C. Average revenue equals marginal cost.
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答案：B
解析：所有市场结构中，利润最大化的条件都是MR = MC。在垄断市场中，P > MR = MC，价格不等于边际成本（A错误）。平均收入等于价格（AR = P），但在垄断市场中AR > MC（C错误）。
选项 判断 解析 A ✗ P = MC仅在完全竞争中成立，垄断市场中P > MC B ✓ MR = MC是所有市场结构下利润最大化的通用条件 C ✗ AR = P，在垄断市场中P > MR = MC，故AR ≠ MC 关联：R12: 企业与市场结构
Q3.
In the short run, which of the following statements is most accurate for a firm in a perfect competition market?
A. The firm will stay in the market if the marginal revenue is higher than the average variable cost.
B. The firm will stay in the market if the marginal revenue is lower than the average variable cost.
C. The firm will leave the market if the marginal revenue is lower than the average total cost.
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答案：A
解析：在短期内，完全竞争企业的停业点为P = AVC。当P(=MR) > AVC时，企业可以覆盖全部可变成本和部分固定成本，应继续经营。当P < AVC时才应停业。P < ATC但P > AVC时企业仍应继续经营（C错误）。
选项 判断 解析 A ✓ MR > AVC意味着企业可以覆盖可变成本，短期应继续经营 B ✗ MR < AVC时企业应停业，因为无法覆盖可变成本 C ✗ MR < ATC但MR > AVC时企业短期仍应经营，仅长期退出 关联：R12: 企业与市场结构
Q4.
Jeff Liu is a hard-working farmer who had 10 acres of land to grow corn and sold harvest in a perfectly competitive market. After introducing an advanced machine, the farmer could dramatically increase farming productivity. To utilize the new machine, the farmer rented two more acres of land to grown corn. If the farmer keeps the output per acres constant and sold out all the corn, the total revenue in this year would mostly rise by:
A. more than 20%.
B. 20%.
C. less than 20%.
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答案：B
解析：在完全竞争市场中，单个企业是价格接受者（price taker），产量变化不影响市场价格。农民从10英亩增加到12英亩，产量增加20%（每英亩产量不变）。由于价格不变，总收入 = 价格 x 数量，也增加20%。
选项 判断 解析 A ✗ 完全竞争市场中单个企业无法影响价格，收入增幅等于产量增幅 B ✓ 产量增加20%，价格不变，总收入恰好增加20% C ✗ 价格不会因单个企业增产而下降，收入增幅不会低于产量增幅 关联：R12: 企业与市场结构
Q5.
A firm does its business in a perfectly competitive market. If the firm can stay in the market in the short run but is expected to exit the market in the long run, which of the following situations is the firm most likely facing now?
A. Average revenue is less than average total cost but more than average variable cost.
B. Marginal revenue is more than average total cost.
C. Price is less than average variable cost.
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答案：A
解析：企业短期继续经营但长期退出，说明AVC < P(=AR) < ATC。企业能覆盖可变成本（不停业）但无法覆盖全部成本（长期亏损退出）。B选项MR > ATC意味着企业盈利，不会退出。C选项P < AVC时企业短期也应停业。
选项 判断 解析 A ✓ AVC < AR < ATC，短期可经营但长期亏损退出 B ✗ MR > ATC意味着企业有经济利润，不会退出 C ✗ P < AVC时企业短期就应停业，不是”短期继续经营” 关联：R12: 企业与市场结构
Q6.
Which of the following statements about economies of scale is least accurate?
A. Diminishing waste and decreasing costs lead to economies of scale.
B. The division of labor leads to economies of scale.
C. Economies of scale refers to the phenomenon that economic profits decrease through expanding production scale.
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答案：C
解析：规模经济是指随着产量扩大，长期平均成本（LRATC）下降的现象，而不是经济利润下降。A正确：减少浪费和降低成本是规模经济的来源。B正确：劳动分工提高效率也是规模经济的来源。
选项 判断 解析 A ✓ 减少浪费、降低成本确实是规模经济的表现 B ✓ 劳动分工是规模经济的重要来源之一 C ✗ 规模经济是平均成本下降，不是经济利润下降 关联：R12: 企业与市场结构
Q7.
The latest quarterly performance express of a listed company briefly disclosed the production situation. The production input cost of the new generation series product X increased by 2.3% and the output increased by 4.7%; The production input cost of classic series product Y increased by 5.1% and the output increased by 4.8%. According to the above information, which of the following statements is most likely to be correct?
A. Product X has increasing returns to scale and product Y has decreasing returns to scale.
B. Product X has decreasing returns to scale and product Y has increasing returns to scale.
C. Product X has increasing returns to scale and product Y has increasing returns to scale.
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答案：A
解析：规模报酬递增：产出增加比例 > 投入增加比例。规模报酬递减：产出增加比例 < 投入增加比例。产品X：投入增加2.3%，产出增加4.7%，产出增幅 > 投入增幅，为递增规模报酬。产品Y：投入增加5.1%，产出增加4.8%，产出增幅 < 投入增幅，为递减规模报酬。
选项 判断 解析 A ✓ X产出增幅(4.7%)>投入增幅(2.3%)为递增；Y产出增幅(4.8%)<投入增幅(5.1%)为递减 B ✗ X和Y的规模报酬判断与实际相反 C ✗ Y的产出增幅小于投入增幅，不是递增规模报酬 关联：R12: 企业与市场结构
Q8.
In a perfectly competitive market, which is the least likely? There are:
A. many sellers.
B. high barrier to entry.
C. identical products.
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答案：B
解析：完全竞争市场的特征包括：大量买家和卖家（A正确）、同质产品（C正确）、无进入/退出壁垒（低壁垒而非高壁垒）。高进入壁垒是垄断或寡头市场的特征，不是完全竞争市场的特征。
选项 判断 解析 A ✓ 完全竞争市场确实有大量卖家 B ✗ 完全竞争市场进入壁垒极低，不是高壁垒 C ✓ 完全竞争市场产品同质 关联：R12: 企业与市场结构
Q9.
Which of the following statements about monopolistic market is least accurate?
A. Economic profit can exist in the long run due to high entry barriers.
B. The product offered by the seller has no close substitute.
C. A monopolist will charge a price as high as possible.
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答案：C
解析：垄断企业并不会将价格定得尽可能高，而是在MR = MC处确定利润最大化的产量和价格。过高的价格会导致需求量大幅下降，反而降低总利润。A正确：高进入壁垒使垄断企业长期可获经济利润。B正确：垄断产品无近似替代品。
选项 判断 解析 A ✓ 高进入壁垒确实使垄断企业长期可获经济利润 B ✓ 垄断市场的产品确实无近似替代品 C ✗ 垄断企业在MR=MC处定价以最大化利润，不是定价越高越好 关联：R12: 企业与市场结构
Q10.
Since Alice’s home-brewed wine was popular with her friends, she decided to open her winery to produce and sell the home-brewed wine. After purchasing equipment with little capital, Alice opened the winery. To increase brand visibility, she put an advertisement in local newspapers. Due to the distinct taste of the wine and the successful advertisement, the demand had far outstripped the supply even though Alice increased the price of the wine several times. Alice most likely faced:
A. Perfect competition.
B. Monopolistic competition.
C. Monopoly.
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答案：B
解析：关键特征：(1)低资本进入壁垒（little capital）；(2)差异化产品（distinct taste）；(3)通过广告建立品牌；(4)有一定定价权（raised price several times）。这些都是垄断竞争市场的典型特征。完全竞争无差异化产品和定价权；纯垄断有高进入壁垒。
选项 判断 解析 A ✗ 完全竞争市场产品同质，无定价权，不需要广告 B ✓ 低进入壁垒+差异化产品+广告+一定定价权=垄断竞争 C ✗ 垄断市场有极高进入壁垒，Alice以少量资本就能进入 关联：R12: 企业与市场结构
Q11.
China Mobile, China Unicom, and China Telecom are the only three main carrier operators in China. All of them provide standardized mobile communication products and homogeneous services. The three carrier operators are most likely to compete in which market?
A. Perfect competition.
B. Oligopoly.
C. Monopoly.
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答案：B
解析：市场中仅有三家主要运营商（少数卖家），提供标准化产品和同质服务。这是寡头市场的典型特征：少量企业、高进入壁垒（电信牌照）、产品可同质或差异化。完全竞争需大量企业，垄断仅有一家。
选项 判断 解析 A ✗ 完全竞争市场有大量卖家，不是只有三家 B ✓ 少量企业+高进入壁垒+同质产品=寡头市场 C ✗ 垄断市场只有一家企业，这里有三家 关联：R12: 企业与市场结构
Q12.
Compared to a perfectly competitive market, what is the unique characteristic of monopolistic competition market?
A. The manufacturer has some pricing power.
B. The manufacturers earn economic profit in the long run.
C. There are a large number of buyers and sellers.
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答案：A
解析：垄断竞争与完全竞争的关键区别在于产品差异化，这赋予企业一定的定价权（pricing power）。C选项两种市场都有大量买卖方。B选项垄断竞争长期经济利润为零（因低进入壁垒），与完全竞争相同。
选项 判断 解析 A ✓ 产品差异化使垄断竞争企业拥有一定定价权，这是与完全竞争的关键区别 B ✗ 垄断竞争长期经济利润也为零，与完全竞争相同 C ✗ 两种市场结构都有大量买卖方，不是独有特征 关联：R12: 企业与市场结构
Q13.
Colgate runs its business in a market with a lot of competitors. To compete with others, Colgate builds two product lines of toothpaste. The materials and process to produce the toothpaste are the same. To distinguish the two product lines, Colgate uses various keywords in the advertisement. For one product line, Colgate highlights the effect of whitening teeth. For another product line, Colgate underlines the desensitization. The market structure is most likely to be:
A. perfect competition.
B. oligopoly.
C. monopolistic competition.
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答案：C
解析：关键特征：(1)大量竞争者；(2)通过广告进行产品差异化（相同材料和工艺但不同营销定位）；(3)品牌竞争。这是垄断竞争的典型特征。完全竞争产品同质无需广告；寡头市场仅少数企业。
选项 判断 解析 A ✗ 完全竞争产品同质，不需要通过广告差异化 B ✗ 寡头市场仅有少数企业，而题目说有大量竞争者 C ✓ 大量竞争者+通过广告进行产品差异化=垄断竞争 关联：R12: 企业与市场结构
Q14.
Which of the following statements about the kinked demand curve model is least accurate?
A. An increase in a firm’s product price will not be followed by its competitors.
B. A decrease in a firm’s product price will be followed by its competitors.
C. The elasticity of demand is greater when price decreases than price increases.
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答案：C
解析：拐折需求曲线模型中：涨价时竞争者不跟随（A正确），企业失去大量客户，需求弹性大（需求曲线较平坦）。降价时竞争者跟随（B正确），企业无法获得更多市场份额，需求弹性小（需求曲线较陡峭）。因此涨价时弹性大于降价时弹性，C说反了。
选项 判断 解析 A ✓ 涨价时竞争者不跟随，这是拐折需求曲线的基本假设 B ✓ 降价时竞争者跟随，这是拐折需求曲线的基本假设 C ✗ 涨价时弹性更大（更弹性），降价时弹性更小（更非弹性），C说反了 关联：R12: 企业与市场结构
Q15.
FZ Cookie is a firm that takes the price set by the dominant company in an oligopolistic market. In an attempt to increase its market share in the industry, the firm instigates a price war by decreasing its price. Which of the following statements is most likely to be the result of the price war?
A. The market share of FZ Cookie will increase.
B. The market share of the dominant company will decrease.
C. The market share of FZ Cookie will decrease.
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答案：C
解析：在寡头市场的价格领导模型中，主导企业有成本优势。当小企业发起价格战时，主导企业可以承受更低的价格。价格战最终会伤害成本较高的小企业（FZ Cookie），其市场份额反而会下降，甚至可能被迫退出市场。
选项 判断 解析 A ✗ 小企业在价格战中处于劣势，无法增加市场份额 B ✗ 主导企业有成本优势，价格战中市场份额不会下降 C ✓ 小企业发起价格战会导致自身亏损加剧，市场份额下降 关联：R12: 企业与市场结构
Q16.
There are two oligopoly firms X and Y in the mobile payment industry of a country. Due to the recent government antitrust regulation, the two firms are facing the following countermeasures and corresponding benefits:
(1) If firm X opens the platform, the annual profit is expected to be $5 billion; If firm Y opens the platform, the annual profit is expected to be $6 billion.
(2) If firm X opens the platform, the annual profit is expected to be $5.8 billion; If firm Y is connected to the supervision system, the annual profit is expected to be $7 billion.
(3) If firm X is connected to the supervision system, the annual profit is expected to be $6.3 billion; If firm Y opens the platform, the annual profit is expected to be $5.8 billion.
(4) If firm X is connected to the supervision system, the annual profit is expected to be $4 billion; If firm Y is connected to the supervision system, the annual profit is expected to be $6.5 billion.
According to the above information, it is inferred that what is the most likely benefit of the Nash equilibrium strategy of firms X and Y?
A. The annual profits of firms X and Y are expected to be $5 billion and $6 billion respectively.
B. The annual profits of firms X and Y are expected to be $5.8 billion and $7 billion respectively.
C. The annual profits of firms X and Y are expected to be $6.3 billion and $5.8 billion respectively.
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答案：B
解析：构建博弈矩阵分析纳什均衡：
Y开放平台 Y接入监管 X开放平台 X:5, Y:6 X:5.8, Y:7 X接入监管 X:6.3, Y:5.8 X:4, Y:6.5 对于X：若Y开放平台，X选接入监管(6.3>5)；若Y接入监管，X选开放平台(5.8>4)。 对于Y：若X开放平台，Y选接入监管(7>6)；若X接入监管，Y选接入监管(6.5>5.8)。 Y的占优策略是接入监管。X知道Y选接入监管，X选开放平台(5.8>4)。 纳什均衡：X开放平台，Y接入监管，利润为(5.8, 7)。
选项 判断 解析 A ✗ 对应(X开放, Y开放)，但Y有动机转向接入监管 B ✓ 对应纳什均衡(X开放平台, Y接入监管) C ✗ 对应(X接入监管, Y开放平台)，但Y有动机转向接入监管 关联：R12: 企业与市场结构
Q17.
An analyst gathered the following market share data for an industry comprised of five companies:
| Company | Market Share (%) |
|---|---|
| Zeta | 35 |
| Yusef | 25 |
| Xenon | 20 |
| Waters | 10 |
| Vlastos | 10 |
The industry’s three-firm Herfindahl-Hirschman index is closest to:
A. 0.185
B. 0.225
C. 0.235
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答案：B
解析：三家企业HHI计算前三大企业市场份额的平方和：
计算过程：
注意：HHI使用小数形式的市场份额（不是百分比）。
选项 判断 解析 A ✗ 计算错误 B ✓ ^2 + 0.25^2 + 0.20^2 = 0.225$ C ✗ 可能是五家企业HHI的计算结果 关联：R12: 企业与市场结构
Q18.
Suppose we have the following statistics:
Industry X: the six-firm Herfindahl-Hirschmann Index is 80%. The market share of companies in the industry changes frequently, and the phenomenon of “new in and old out” often occurs.
Industry Y: the six-firm Herfindahl-Hirschmann Index is 78%. The companies in the industry were established earlier and the market share is relatively stable.
Which of the following statements is most likely to be correct?
A. Industry X is a perfectly competitive industry.
B. Industry Y is a monopoly industry.
C. Industry Y may have a higher degree of monopoly than X.
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答案：C
解析：虽然行业X的HHI(80%)略高于Y(78%)，但HHI有其局限性。行业X市场份额频繁变动、企业进出频繁，说明竞争激烈。行业Y市场份额稳定、企业建立较早，说明可能存在更高的进入壁垒和垄断程度。单纯用HHI无法完全反映市场竞争程度。
选项 判断 解析 A ✗ HHI为80%过高，不符合完全竞争市场特征 B ✗ HHI为78%且有六家企业，不是垄断市场 C ✓ 尽管Y的HHI略低，但其稳定的市场份额和高壁垒暗示更高垄断程度 关联：R12: 企业与市场结构