不完全競爭

1. 不完全競爭

2. 為何有許多檳榔攤？客人似乎不多，如何賺取利潤？為何有許多檳榔攤？客人似乎不多，如何賺取利潤？ • 為何Coca Cola, Nike，泛亞要拍那麼多廣告？ • 金價天天在變，為什麼有些東西價格卻很少改變？ • 米酒VS青菜

3. 9-1 【 不完全競爭市場理論】 主要是由英國 的羅賓遜夫人（Robinson）與美國的秦伯霖（Chamberlin）分別發展出來的。由於在實際的經濟社會中，廠商對價格多多少少具有決定能力，所面對的市場既非完全開放（如：完全競爭市場），也不是全然封閉（如：完全獨占市場），因此，實際經濟社會的市場形態多為「不完全競爭市場」。

4. 不完全競爭市場包含了「獨占性競爭市場」與「寡占市場」兩種基本形態，兩者的相同點為：個別廠商對價格都具有影響力；而相異點在於獨占性競爭市場的廠商人數眾多，而寡占市場通常由少數幾個廠商控制整個產業。 9-1

5. 龔斷性競爭Monopolistic Competition • 廠商數目多，買者多，每個人都只有很少的占有率 • 自由進出 • 完全資訊 • Firms compete on product quality, price, and marketing • 異質性產品：如洗髮精、泡麵、蔥油餅

6. PC War Games • Each PC maker tells us that they have the best product at the best price. • Just two big chip makers produce almost all the processor and memory chips in our PCs. • Firms in these markets are neither price takers like those in perfect competition, nor are they protected from competition by barriers to entry like a monopoly. • How do such firms choose the quantity to produce and price?

7. Monopolistic Competition • Monopolistic competition is a market with the following characteristics: • A large number of firms. • Each firm produces a differentiated product. • Firms compete on product quality, price, and marketing. • Firms are free to enter and exit the industry.

8. Large Number of Firms implies • Each firm has only a small market share and therefore has limited market power to influence the price of its product. • Each firm is sensitive to the average market price, but no firm pays attention to the actions of the other, and no one firm’s actions directly affect the actions of other firms. • Collusion, or conspiring to fix prices, is impossible.

9. Product Differentiation • each firm makes a product that is slightly different from the products of competing firms.

10. Competing on Quality, Price, and Marketing • Quality includes design, reliability, and service. • Because firms produce differentiated products, each firm has a downward-sloping demand curve for its own product. • But there is a tradeoff between price and quality. • Differentiated products must be marketed using advertising and packaging.

11. Entry and Exit • There are no barriers to entry in monopolistic competition, so firms cannot earn an economic profit in the long run.

12. Examples of Monopolistic Competition • The red bars refer to the 4 largest firms. • Green is the next 4. • Blue is the next 12.

13. Short-Run Economic Profit • A firm that has decided the quality of its product and its marketing program produces the profit maximizing quantity at which its marginal revenue equals its marginal cost (MR = MC). • Price is determined from the demand curve for the firm’s product and is the highest price the firm can charge for the profit-maximizing quantity.

14. (一) 獨占性競爭廠商所面對的需求曲線 9-2 獨占性競爭市場的短期均衡 • 一條由左上方向右下方延伸的需求曲線。 • 獨占性競爭廠商所面對的需求曲線較獨占廠商平坦些。 • 獨占性競爭廠商的獨占性愈強，其所面對的曲線愈陡峭，反之則愈平坦。

15. Output and Price in Monopolistic Competition • It operates much like a single-price monopolist. • The firm produces the quantity at which price equals marginal cost and sells that quantity for the highest possible price. • It earns an economic profit (as in this example) when P > ATC.

16. 獨占性競爭市場的長期均衡 • Zero Economic Profit • In the long run, economic profit induces entry. • And entry continues as long as firms in the industry earn an economic profit—as long as (P > ATC). • In the long run, a firm in monopolistic competition maximizes its profit by producing the quantity at which its marginal revenue equals its marginal cost, MR = MC.

17. 長期均衡 • P = AC • 利潤為零，但不在LRAC最低點

18. 9-2 獨占性競爭市場的長期均衡 E

19. Output and Price in Monopolistic Competition • As firms enter the industry, each existing firm loses some of its market share. The demand for its product decreases and the demand curve for its product shifts leftward. • The decrease in demand decreases the quantity at which MR = MC and lowers the maximum price that the firm can charge to sell this quantity. • Price and quantity fall with firm entry until P = ATC and firms earn zero economic profit.

20. Output and Price in Monopolistic Competition • If firms incur an economic loss, firms exit to restore the long-run equilibrium just described.

21. Monopolistic Competition and Efficiency • Firms in monopolistic competition are inefficient and operate with excess capacity.

22. Excess Capacity超額產能理論 • AC最低點是最適產量，而獨占性競爭長期均衡卻是在切點，故通常有產能的浪費。

23. Excess Capacity • 是否應鼓勵所有公司合併？ • 產量不變而總成本可能減少 • 消費者的選擇會減少 • 很多的檳榔攤、小吃店，使顧客較為方便　　　

24. excess capacity • Because price equals the marginal benefit, marginal cost is less than marginal benefit. • Underproduction in monopolistic competition creates deadweight loss.

25. capacity output • A firm’s capacity output is the output at which average total cost is at its minimum. • At the long-run profit maximizing output, price equals average total cost.

26. excess capacity • If MC < ATC, then the ATC curve is falling. • With falling ATC, output is less than capacity output. • Goods are not produced at the minimum unit cost of production in the long run.

27. Product Development and Marketing • Innovation and Product Development • To keep earning an economic profit, a firm in monopolistic competition must be in a state of continuous product development. • New product development allows a firm to gain a competitive edge, if only temporarily, before competitors imitate the innovation.

28. 1.就生產效率觀點而言 獨占性競爭廠商的長期均衡點並非長期平均成本的最低點，因此不是最適生產規模（小於最適規模），表示廠商沒有充分利用資源。 2.就資源配置觀點而言 當P=MC時，資源達到最佳配置效率，但在獨占性競爭之情形下，依據MR=MC均衡條件，得出P>MC，故價格偏高，產量偏低。

29. 3.就消費福利觀點而言 獨占性競爭場商的產品具有差異性，可以滿足個別消費者的偏好，增進消費者福利，但是消費者必須付出較高的價格是其缺點。

30. Innovation • Innovation is costly, but it increases total revenue. • Firms pursue product development until the marginal revenue from innovation equals the marginal cost of innovation. • Production development may benefit the consumer by providing an improved product, or it may only create the appearance of a change in product quality. • Regardless of whether a product improvement is real or imagined, its value to the consumer is its marginal benefit, which is the amount the consumer is willing to pay for it.

31. Marketing行銷和廣告的作用 • A firm’s marketing program uses advertising and packaging as the two principal methods to market its differentiated products to consumers. • Firms in monopolistic competition incur heavy marketing and advertising expenditures to enhance the perception of quality differences between their product and rival products. These costs make up a large portion of the price for the product.

32. Product Development and Marketing • Cleaning supplies and toys top the list at almost 15 percent.

33. Selling Costs and Total Costs • Selling costs, like advertising expenditures, fancy retail buildings, etc. are fixed costs. • Average fixed costs decrease as production increases, so selling costs increase average total costs at any given level of output but do not affect the marginal cost of production. • Selling efforts such as advertising are successful if they increase the demand for the firm’s product.

34. Product Development and Marketing • With advertising, the firm produces 130 units of output at an average total cost of $160.

35. advertising has a short run effect • Economic profit leads to entry, which decreases the demand for each firm’s product in the long run. • To the extent that advertising and selling costs provide consumers with information and services that they value more highly than their cost, these activities are efficient.

36. 廣告 • Why not Perfect Competition firm? • 相對市場非常少，故無需要 • 產品identical 廣告增加成本，卻可能導向其他廠商

37. Oligopoly • Oligopoly is a market in which a small number of firms compete. • In oligopoly, the quantity sold by one firm depends on the firm’s own price and the prices and quantities sold by the other firms. • The response of other firms to a firm’s price and output influence the firm’s profit-maximizing decision.

38. 寡占市場的特質 互相牽制，互相依賴 寡占市場是由少數幾家廠商控制整個產業，每家廠商的行動都會影響到其他廠商的利益，因此寡占廠商彼此間會互相牽制、也相互依賴。

39. The Kinked Demand Curve Model拗折的需求線 • In the kinked demand curve model of oligopoly, each firm believes that if it raises its price, its competitors will not follow, but if it lowers its price all of its competitors will follow.

40. 拗折需求曲線又稱「扭結需求曲線」，此理論主要是用來解釋寡占廠商價格僵固的現象，由美國經濟學家史威吉（P. M. Sweezy）於1939年所提出。根據該模型認為，寡占廠商的市場需要曲線，不同於其他市場的生產者，而具有特殊形態，由於此一特殊形態，使得寡占市場的價格相當穩定，不易變化。

41. 拗折的需求線(sticky price)價格僵硬化模型 基本假設：跟跌不跟漲 即指：當某一寡占廠商提高價格時，其它廠商不會跟著抬高價格（此為不跟漲），可是當某一寡占廠商降低價格時，其它廠商們擔心市場會被掠奪，故會馬上調低價格（此為跟跌）。 • 即使MC有所改變，價格不變(穩定的價格取向)

42. Oligopoly • The demand curve that a firm believes it faces has a kink at the current price and quantity.

43. Oligopoly • Above the kink, demand is relatively elastic because all other firm’s prices remain unchanged. • Below the kink, demand is relatively inelastic because all other firm’s prices change in line with the price of the firm shown in the figure.

44. 穩定的價格 • Fluctuations in MC that remain within the discontinuous portion of the MR curve leave the profit-maximizing quantity Q and price P unchanged.

45. 9-3 (三) 拗折的需要曲線 DB DA A K P0 C E DA D B MRB MRA Q0 DB MR

46. 9-3 (四) 拗折需求曲線解釋價格的僵固性 由於廠商間的競爭策略為「跟跌不跟漲」，所以需求曲線有拗折點的存在，故其對應AKB需求曲線的邊際收益曲線MR，會在拗折點所決定的產量下有斷折的情形，稱為邊際收益缺口(marginal revenue gap)。

47. 9-3 由拗折的需求曲線可知，當寡占廠商建立某價格後，若MC變動不大，則其價 格不會改變，造成了價格僵固性（price rigidity）的現象。在實際社會中不乏有這方面的例子，如汽車、電視等產品的價格就不會像日常生活中的蔬菜水果或魚類的價格經常在改變，這主要是因為廠商們對於價格的設定，除非不得已否則都會儘量採按兵不動的策略。 (五) 結論

48. Oligopoly • The beliefs that generate the kinked demand curve are not always correct and firms can figure out this fact • If MC increases enough, all firms raise their prices and the kink vanishes. • A firm that bases its actions on wrong beliefs doesn’t maximize profit.

49. 2. Dominant Firm Oligopoly 價格領袖 • In a dominant firm oligopoly, there is one large firm that has a significant cost advantage over many other, smaller competing firms. • The large firm operates as a monopoly, setting its price and output to maximize its profit. • The small firms act as perfect competitors, taking as given the market price set by the dominant firm.

50. 寡占市場中的廠商可能為了避免獨自訂價的麻煩，以及所訂價格可能引起競爭者的不良反應等因素，往往不自行訂價，而是參考某一廠商的價格，再決定自己的價格。被其他廠商作為價格依據的廠商，稱為價格領袖或價格領導者( price leader )。而其他追隨此價格領袖的廠商可稱為價格跟隨者(price followers)。