12 CHAPTER 獨占競爭與寡占

C H A P T E R C H E C K L I S T 學習本章後，您將能： 眾多彼此競爭的廠商 廠商生產差異化的產品 1 廠商生產差異化的產品 2 廠商價格、品質與行銷上的兢爭 3 廠商可以自由加入或退出市場 4

12.1 獨占競爭的定義 獨占競爭 的特徵為： 眾多彼此競爭的廠商 廠商生產差異化的產品 廠商在價格、品質與行銷上的競爭 廠商可以自由加入或退出市場 Students have no difficulty seeing monopolistic competition in the world all around them. Emphasize that the work they’ve just done understanding the models of perfect competition and monopoly are not wasted because the real-world situation of monopolistic competition, as its name implies, is a mixture of both extremes. Some of what they learned in each of the two previous chapters survives and operates in the middle ground of monopolistic competition.

眾多廠商 12.1 獨占競爭的定義 如同完全競爭市場，獨占競爭市場包含眾多廠商 個別廠商市場占有率小 廠商對市場均衡價格影響力小，且無法主宰市場 個別廠商行為不會直接影響其他廠商

產品差異化 12.1 獨占競爭的定義 產品差異化 指創造自家產品與競爭對手間的些微差異 差異化的產品具有密切替代品，但沒有完全替代品 因此價格上漲將導致需求量減少 Product differentiation is the heart of the space between monopoly and competition. An old ice-cream on the beach analogy really nails down the idea of product differentiation and explains how monopolistic competition fills the space between monopoly and perfect competition. Draw a line on the blackboard and label the two ends A and B. Tell the students that the line represents a long beach along which beachgoers are uniformly spaced. An ice-cream vendor decides to set up shop on the beach—the only one. Where will she locate? The students will quickly see that the center—midway between A and B is the spot that will get most customers because the cost of an ice-cream is the market price plus the walking time to get it (remind them that the beach is very long!) Now a second ice-cream vendor opens up. Where does he locate? With a bit of help, the students will see that the best spot is right next to the first one. With one producer, there is monopoly and no variety—no product differentiation. With two producers, there is still no differentiation— technically, there is minimum differentiation. Now suppose a third and fourth ice-cream vendor come along. Where do they locate? At the ends of the beach at A and B. They differentiate as much as possible from each other and from the first two. Further entry has new ice-cream vendors locating in the middle of the gaps between the existing ones, always going into the widest gap. If the market could stand the competition, eventually, there would be ice-cream vendors so close to each other all along the beach that the members of any adjacent group were indistinguishable to a customer. Product differentiation would have been pushed to the point that there is no “space” for additional variety and the market would look like perfect competition. Real products are like the beach example. Talk about sports shoes, breakfast cereals, and any other goods that interest you and for which there are good locally observable examples and encourage the students to see that they are like the beach example. The variety of products fill the available variety “space.”

價格、品質與行銷的競爭 12.1 獨占競爭的定義 品質 設計、耐用、提供的服務與產品的普及程度 價格 由於產品的差異化，獨占競爭廠商面對負斜率的需求曲 線，必須面臨價格與數量的取捨 行銷 廣告與包裝

15.1 獨占競爭的定義 自由加入與退出 沒有加入市場的障礙 獨占競爭廠商長期下的經濟利潤等於 0

四大廠商集中率 指產業前四大廠商的總收入占整個產業總收入的百分比 12.1 獨占競爭的定義 四大廠商集中率 四大廠商集中率 指產業前四大廠商的總收入占整個產業總收入的百分比 完全競爭市場的四大廠商集中率趨近於 0，獨占市場的四大廠商集中率等於 100% 集中率大於 60%，代表由少數廠商主宰的寡占市場 集中率小於 40%，代表獨占競爭市場

12.1 獨占競爭的定義 Herfindahl-Hirschman 指數 Herfindahl-Hirschman 指數 (HHI) 為前五十大廠商市場占有率的平方和 例如，某市場只有四家廠商，市場占有率分別為 50%、25%、15% 與 10%，則 HHI = 502 + 252 + 152 + 102 = 3,450 HHI 值低於1,000 為競爭或獨占競爭市場，HHI 值介於1,000 與 1,800 為適度競爭或獨占競爭市場，HHI 值大於 1,800 為缺乏競爭

12.1 產量與價格決定 廠商利潤極大化的決策 獨占競爭廠商的價格與產量決策類似獨占廠商 圖12.1 獨占競爭的價格與產量

12.1 產量與價格決定 1. 利潤極大化發生在 MR = MC. 2. 利潤極大化的產量等於 125 件/天 3. 利潤極大化的價格為 $75 /件 While students have gotten familiar with the demand, marginal revenue, and marginal cost curves over the past two chapters, still take the time to point out the curves as you draw them. Use actual numbers for quantity and price Unlike the case of perfect competition, the demand curve for a firm’s differentiated product in monopolistic competition is downward sloping. Remind the students about the ceteris paribus condition that defines a demand curve. Along the demand curve for Nike tennis shoes, the prices of Adidas, Fila, Head, K Swiss, Prince, Reebok, and Wilson tennis shoes are constant. Some people prefer Nike to the other brands and will pay a bit more for Nike. Other people prefer some other brand and will buy Nike only if its price is low enough. Buyers have brand preferences, but they will switch brands if price differences are large enough. So the higher the price of a Nike shoe, the prices of the other brands remaining the same, the smaller is the quantity of Nike shoes demanded. ATC 為 $25 /件 4. 經濟利潤為 $6,250 /天

長期的經濟利潤等於零 12.1 產量與價格決定 經濟利潤吸引廠商加入市場，經濟損失迫使部分廠商退 出市場 經濟利潤吸引廠商加入市場，經濟損失迫使部分廠商退 出市場 廠商加入市場，消費者對現存廠商的需求減少 部分廠商退出市場，消費者對現存廠商的需求上升 長期下來，廠商只賺取正常利潤 圖12.2 長期的產量與價格

12.1 產量與價格決定 1. 利潤極大化的產量等於 75 件/天 2. 價格等於 $50 件，也等於平均總成本 3. 經濟利潤等於 0 Students seem to have a bit of trouble appreciating that entry and exit change the demand for a firm’s product. Explain this effect by sticking with the tennis shoes example. Explain that the demand for Nike tennis shoes changes and the demand curve for Nike tennis shoes shifts if other firms enter or exit. If Tommy Hilfiger and the Gap started to make tennis shoes, some of Nike’s former customers would switch to these two new brands, and the demand for Nike shoes would decrease. The demand curve for Nike shoes would shift leftward. If Adidas, Fila, and Reebok stopped making tennis shoes, some of their former customers would switch to like, and the demand for Nike shoes would increase. The demand curve for Nike shoes would shift rightward. 3. 經濟利潤等於 0

12.1 產量與價格決定 產量過剩 廠商的 產量過剩 是指廠商的產量低於平均總成本最低時 的產量 廠商的 效率規模 是平均總成本最低時的產量 廠商的 產量過剩 是指廠商的產量低於平均總成本最低時 的產量 廠商的 效率規模 是平均總成本最低時的產量 加成 廠商的 加成 代表價格大於邊際成本的幅度

12.1 產量與價格決定 1. 效率規模為 100 件/天 2. 廠商的產量低於效率規模，廠商的產能過剩 3. 價格 4. 邊際成本 5. 加成 6. 產生無謂損失

創新與產品發展 12.2 產品發展與行銷 為了享有經濟利潤，獨占競爭廠商必須一直發展新產品，否則模仿者與新廠商的加入將侵蝕經濟利潤 成本與產品創新的收入 廠商必須以邊際分析的方式來平衡成本與收入

12.2 產品發展與行銷 效率與產品創新 當產品發展的額外支出產生等量的額外收入，亦即產品 發展的邊際成本等於邊際收入時，廠商在產品發展上達 成利潤極大化

廣告 廣告成本與總成本 廣告成本為固定成本 12.2 產品發展與行銷 獨占競爭的廠商花費大量支出在廣告及包裝產品上 廣告的平均成本隨著產量增加而遞減 圖12.4 廣告成本與總成本

12.2 產品發展與行銷 1. 當廣告成本加入 2. 生產的平均總成本 3. 平均總成本增加的幅度隨著產量增加而遞減

12.2 產品發展與行銷 4. 如果廣告使得銷售量由 25 件/天增加至 100 件/天，則平均總成本由 $60 /件下跌至 $40 /件

12.2 產品發展與行銷 廣告與需求 廣告與其他對銷售的努力改變了產品的需求 其影響為複雜的： 廠商預期自家產品的需求會因為廣告而增加 所有的廠商皆從事廣告，則廠商數目增加，個別廠 商面對的需求減少，需求曲線變得較有彈性 價格與加成幅度可能變小

12.3 何謂寡占 介於獨占與完全競爭的另一種市場型態 寡占的特徵為： 少數廠商彼此競爭 自然或法律障礙阻止新廠商的加入

12.3 何謂寡占 少數廠商 與獨占競爭與完全競爭相比，寡占市場由少數廠商組成 每家廠商的市占率高 廠商彼此相互依存來面對勾結的誘惑

12.3 何謂寡占 勾結的誘惑 當少數廠商分享市場時，藉由形成類似獨占的卡特爾組 織而增加利潤 當少數廠商分享市場時，藉由形成類似獨占的卡特爾組 織而增加利潤 卡特爾 是指一群廠商彼此勾結、限制產量、提高價格與 增加經濟利潤 卡特爾在許多國家是不合法的 然而國際上最知名的卡特爾為石油輸出國家組織

12.3 寡占的可能結果

12.3 寡占的可能結果 卡特爾達成獨占結果 假設波音與空中巴士兩家公司行成卡特爾，並採取單一定價的行為 如果廠商可以同意生產獨占的產量為 6 架飛機/週，經濟利潤為 $7,200 萬

完全競爭結果 12.3 寡占的可能結果 均衡發生在邊際收入曲線與需求曲線的交點 數兩為12 架飛機/週，價格為 $100 萬/架 圖12.5 雙頭寡占的飛機市場

12.3 寡占的可能結果

卡特爾瓦解 12.3 寡占的可能結果 波音公司增加每週產量至 4 架飛機 波音公司增加每週產量至 4 架飛機 波音的經濟利潤增加至 $4000 萬，空中巴士的利 潤則降為 $3000 萬

12.3 寡占的可能結果 空中巴士公司增加每週產 量至 4 架飛機 對空中巴士而言，此結果使 其經濟利潤增加 $200 萬 空中巴士公司增加每週產 量至 4 架飛機 對空中巴士而言，此結果使 其經濟利潤增加 $200 萬 對波音公司而言， 此結果使 其經濟利潤減少 $800 萬

12.3 寡占的可能結果 波音公司增加每週產量至 5 架飛機 如果波音增加產量至 5 架 飛機/週，其經濟利潤減少 波音公司增加每週產量至 5 架飛機 如果波音增加產量至 5 架 飛機/週，其經濟利潤減少 同樣地， 如果空中巴士增 加產量至 5 架飛機/週，其 經濟利潤減少

12.4 賽局理論 賽局理論 為經濟學家研究策略行為的主要工具，策略行為為瞭解彼此的行為相互牽動，而且將他人的預期行為納入決策的考量

何謂賽局 12.4 賽局理論 囚犯兩難 所有的賽局都有三種特徵： 規則 策略 報償 顯示兩囚犯間為何難以互相合作的一場賽局 The prisoners’ dilemma is a great way to start this lecture. Tell students they get to play a game and get two students to volunteer to be the “criminals.” Give the entire class the story and rules. Don’t use a payoff matrix at this point, just write the options on the board. Then send one of your volunteers out of the room. Ask the remaining student what strategy he or she will take. Get your class to help. It usually takes a few minutes for everyone to agree that confessing is the best strategy. Send the first student from the room and then call in the second student. Ask this student what he or she will do. Because the class already knows what the first student has done, encourage them not to tell. Aid the students as they move toward choosing the equilibrium. Encourage students to remember this gaming strategy because it is the same material that you’ll use to describe a firm’s behavior. You can actually play the prisoner’s dilemma game online. A good Web version of the game can be found on a site operated by a group called Serendip at Bryn Mawr College in Pennsylvania. The URL for the web site is http://serendip.brynmawr.edu/playground/pd.html. If you can use the Web in your classroom, open two browsers and go to this site twice. Get two teams trying to beat Serendip.

囚犯兩難 12.4 賽局理論 亞特與包伯在偷車時被當場被逮，將服刑 2 年 檢察官懷疑他們可能涉及兩個月前的銀行搶案 檢察官缺乏證據，於是決定讓這兩名囚犯進行一場賽局

12.4 賽局理論 規則 囚犯待在不同房間，彼此無法溝通聯繫 如果兩人都承認犯案，每人只要服刑 3 年 如果一人承認，而共犯否認，則承認者將只服刑 1 年，否認者則服刑 10 年 如果兩人都否認，則只服偷車的罪刑 2 年

12.4 賽局理論 策略 策略 為賽局中參賽者可能的行為 此囚犯兩難的策略為： 承認銀行搶案 否認銀行搶案

報償矩陣 是每位參賽者各種可能策略組合下的報償一覽 表 12.4 賽局理論 報償 四種結果： 皆承認 皆否認 亞特承認而包伯否認 包伯承認而亞特否認 報償矩陣 是每位參賽者各種可能策略組合下的報償一覽 表

12.4 賽局理論 亞特與包伯的納許均衡為皆承認 並非最佳結果 囚犯兩難的賽局均衡並非兩人的最佳結果

雙頭寡占的兩難 12.4 賽局理論 每家公司皆有兩種策略： 每週生產 3 架飛機 每週生產 4 架飛機 The duopolist’s dilemma game on pages 406-408 and revisited on pages 413–414 has been carefully designed to get the maximum payoff from the knowledge your students have of the perfect competition and monopoly results of the two preceding chapters and to introduce them to game theory in a setting that is as close to the previously studied settings as possible. Instead of asserting a payoff matrix on pages 413-414, the numbers in the matrix come directly from monopoly profit-maximizing and competitive outcomes calculated on the earlier pages. You need to do a bit of work to generate the payoff numbers, but the whole story hangs together so much better when the student can see where the numbers come from and can see the connection between the oligopoly set up and those of competition and monopoly. Start with Figure 16.2 on page 396 and after you’ve explained the cost and demand conditions shown in the figure, ask the students what they think the price and quantity will be in this industry. There will be differences of opinion. This diversity of opinion motivates the need for a model of the choices the firms make.

12.4 賽局理論 因為每家公司皆有兩種策略，因此有 4 種可能組合： 皆生產 3 架飛機 (獨占結果) 皆生產 4 架飛機 空中巴士生產 3 架，波音生產 4 架飛機 空中巴士生產 4 架，波音生產 3 架飛機

12.4 賽局理論 報償矩陣 表12.6 雙頭寡占賽局的 報償矩陣

12.4 賽局理論 雙頭寡占的均衡 皆每週生產 4 架飛機 同囚犯兩難，雙頭寡占 的均衡得到的非最佳結 果 同囚犯兩難，雙頭寡占 的均衡得到的非最佳結 果 Determining the Nash equilibrium of a game is often difficult for students. Try to make the game more “practical” by pointing out to the students that in the real world, real firms are almost always doing ”what if” analyses and that game theory is well designed for answering these sorts of “what if” questions. In the Airbus/Boeing game in the text, the two companies are trying to determine how many airplanes they should produce if their competitor produces 3 airplanes or if their competitor produces 4 airplanes. You can illustrate the equilibrium by starting with Airbus and stating that Airbus wants to determine what it should do if Boeing produces 4 airplanes. Then, after determining that Airbus will produce 4 airplanes, do the next “what if” by looking what Airbus should do if Boeing produces 3 airplanes. In this case, Airbus again wants to produce 4 airplanes. Therefore Airbus’s “what if” analysis has led to the conclusion that regardless of Boeing’s decision, Airbus wants to produce 4 airplanes. You can conduct the same “what if” for Boeing’s choices and determine that Boeing, too, will produce 4 airplanes regardless of Airbus’s choice.

12.4 賽局理論 寡占的廣告與研發賽局 可口可樂與百事可樂的廣告賽局，P&G 與 金百利的研發 賽局也同於囚犯兩難的賽局

12.4 賽局理論 廣告賽局 可口可樂與百事可樂的策略：廣告與不廣告 表12.7 廣告賽局的報償矩陣

12.4 賽局理論 此賽局的納許均衡為兩家公司皆廣告

12.4 賽局理論 研發賽局 P&G 與金百利的策略： 研發與不研發 表12.8 研發賽局的報償 矩陣

12.4 賽局理論 此賽局的納許均衡為兩 家公司皆研發

重覆的賽局 12.4 賽局理論 真實世界的賽局通常是重覆進行 重覆的賽局中，參賽者可以懲罰對手 真實情況下，雙頭寡占廠商可能學習如何合作以享受獨 占利潤

12.4 賽局理論 第 1 週：假設波音考慮生產 4 架飛機 波音的利潤將由 $3,600 萬增加至 $4,000 萬，而空中巴士的利潤將由 $3,600 萬減少至 $3,000 萬 第 2 週：空中巴士生產 4 架飛機來懲罰波音

12.4 賽局理論 實際上，雙頭寡占的賽局能否重複，取決於參賽者的數 目、偵察與懲罰的難易度。 參賽者越多，則越難維繫獨占的結果

效率數量發生在價格 (邊際利益) 等於邊際成本之際 若寡占廠商進行重覆的賽局，則產生獨占的結果 12.4 賽局理論 寡占缺乏效率 效率數量發生在價格 (邊際利益) 等於邊際成本之際 若寡占廠商進行重覆的賽局，則產生獨占的結果 如果寡占廠商彼此不合作，也不需要將價格降低至邊際成 本。因此寡占通常缺乏效率。