Chapter 8 Profit Maximization and Competitive Supply Chapter

Chapter 8 Profit Maximization and Competitive Supply 競爭市場的均衡與供給 Chapter 8

8. 1 完全競爭市場 Perfectly Competitive Markets n 特徵 1) Price taking – 短期 (Product homogeneity) 2) Free entry and exit – 長期 Chapter 8 3

8. 3 邊際收益, 邊際成本, 利潤最大 n 利潤 Profit ( ) = Total Revenue - Total Cost Chapter 8 7

短期利潤最大 Total Revenue Cost, Revenue, Profit ($s per year) R(q) Slope of R(q) = MR 0 Output (units per year) Chapter 8 8

短期利潤最大 C(q) Cost, Revenue, Profit $ (per year) Total Cost Slope of C(q) = MC 為何產量為零時, 成本大於零? 0 Output (units per year) Chapter 8 9

邊際收益, 邊際成本, 利潤最大 n 比較 R(q)與C(q) n 當產量是在 0 至 q 0: n C(q)>R(q) n n n Cost, Revenue, Profit ($s per year) C(q) A Negative profit FC + VC > R(q) B MR > MC n 產量增加 利潤提高 0 q* Output (units per year) Chapter 8 10

邊際收益, 邊際成本, 利潤最大 n 比較 R(q)與C(q) n 問題: 為何產量 為零時, 利潤是 負的? Cost, Revenue, Profit $ (per year) C(q) A R(q) B 0 q* Output (units per year) Chapter 8 11

邊際收益, 邊際成本, 利潤最大 n 比較R(q)與C(q) n 產量在: q 0 - q* n R(q)>C(q) n MR > MC Cost, Revenue, Profit $ (per year) C(q) A R(q) B 產量增加 利潤提高 0 q* Output (units per year) Chapter 8 12

邊際收益, 邊際成本, 利潤最大 n 比較R(q)與C(q) n 產量: q* Cost, Revenue, Profit $ (per year) C(q) A R(q)>C(q) n MR = MC n Profit is maximized n R(q) B 0 q* Output (units per year) Chapter 8 13

邊際收益, 邊際成本, 利潤最大 n 比較R(q)與C(q) q*: n R(q)> C(q) n 產量超過 Cost, Revenue, Profit $ (per year) C(q) A R(q) B MC > MR n Profit is decreasing n 0 q* Output (units per year) Chapter 8 15

邊際收益, 邊際成本, 利潤最大 n 因此: Cost, Revenue, Profit $ (per year) C(q) A n 利潤最大時, 是在: MC = MR R(q) B 0 q* Output (units per year) Chapter 8 16

競爭市場的需求線 Price $ per bushel Firm $4 d Industry $4 D 100 200 Output (bushels) Chapter 8 100 Output (millions of bushels) 21

競爭廠商, 短期均衡, 有利潤 MC Price 60 ($ per unit) 50 40 Lost profit for qq < q * A D Lost profit for q 2 > q * ATC C B 30 AVC At q*: MR = MC and P > ATC q 1 : MR > MC and q 2: MC > MR 20 and q 0: MC = MR but MC falling 10 0 AR=MR=P 1 q 0 2 3 4 5 6 Chapter 8 7 q 1 8 q* 9 q 2 10 11 Output 24

A Competitive Firm – Positive Profits Price 50 40 Profit per unit = PAC(q) = A to B MC Total Profit = ABCD A D AR=MR=P ATC 30 C Profits are determined by output per unit times quantity AVC B 20 10 0 1 2 3 4 5 6 Chapter 8 7 q 1 8 q* 9 q 2 10 11 Output 25

A Competitive Firm – Losses MC Price ATC B C D A q *: 在 MR = MC 但 P < ATC 損失 (P-AC) x q* 或 ABCD P = MR AVC q* Chapter 8 Output 26

煉銅廠的短期產出 Cost (dollars per item) 1400 Observations • Price between $1140 & $1300: q = 600 • Price > $1300: q = 900 • Price < $1140: q = 0 P 2 1300 P 1 1200 Question Should the firm stay in business when P < $1140? 1140 1100 0 300 600 Chapter 8 900 Output (tons per day) 28

8. 5 競爭廠商的短期供給線 Price ($ per unit) MR = MC 決定 利潤最大的產量, 只要變動成本能賺回來就好 MC P 2 ATC P 1 AVC What happens if P < AVC? P = AVC q 1 Chapter 8 q 2 Output 30

競爭廠商的短期供給線 n Observations: P = MR n MR = MC n P = MC n n 供給就是價格與供給量的關係. 因此: If P = P 1, then q = q 1 n If P = P 2, then q = q 2 n Chapter 8 31

競爭廠商的短期供給線 Price ($ per unit) S = MC above AVC MC P 2 ATC P 1 AVC P = AVC Shut-down q 1 Chapter 8 q 2 Output 32

要素價格改變 Price ($ per unit) MC 2 Savings to the firm from reducing output 要素成本增加, MC 升到 MC 2 產量 q 減至 q 2. MC 1 $5 q 2 Chapter 8 q 1 Output 35

石化產品的短期生產 Cost ($ per barrel) 27 提煉石化產品SMC 隨產量有階段變化, SMC 因提煉技術不同 26 產量多少? 當 P = $23? P = $24 -$25? 25 24 23 8, 000 9, 000 10, 000 Chapter 8 11, 000 Output (barrels/day) 36

市場短期供給線 MC 1 $ per unit MC 2 MC 3 S 水平加線 P 3 P 2 P 1 2 4 5 7 8 10 Chapter 8 15 Q 21 38

世界銅產業 (1999) Country Annual Production (thousand metric tons) Australia Canada Chile Indonesia Peru Poland Russia United States Zambia 600 710 3660 750 420 450 1850 280 Chapter 8 Marginal Cost (dollars/pound) 0. 65 0. 75 0. 50 0. 55 0. 70 0. 80 0. 50 0. 70 0. 55 39

世界銅產業 (2001) Country Annual Production (thousand metric tons) Australia Canada Chile Indonesia Peru Poland Russia United States Zambia 900 620 4650 1080 560 450 550 1340 320 Chapter 8 Marginal Cost (dollars/pound) 0. 65 0. 75 0. 50 0. 55 0. 70 0. 80 0. 50 0. 70 0. 55 40

銅的短期世界供給 Price ($ per pound) 0. 90 MCPo 0. 80 MCCa 0. 70 MCA 0. 60 MCJ, MCZ MCC, MCR 0. 50 0. 40 MCP, MCUS 0 2000 4000 6000 8000 10000 Production (thousand metric tons) Chapter 8 41

生產者剩餘 Price ($ per unit of output) Producer Surplus MC 此例中, q* MC = MR. 在 0 與 q* 之間, 每一單位都是MR > MC AVC B A D 0 P C q* Chapter 8 另一種算法: TVC=ODCq*. TR=OABq*. PS=ABCD. Output 43

短期市場供給線 n Producer Surplus in the Short-Run 利潤 = π = TR – TVC – TFC 書上: 利潤 = π = R – VC – FC Chapter 8 44

市場的生產者剩餘 Price ($ per unit of output) S 市場(產業)生產者剩餘 是價格與供給線所夾面積 P* Producer Surplus D Q* Chapter 8 Output 46

8. 7長期均衡產量 (Choosing Output in the Long Run) n 長期, 任何要素數量均可變, 包括規模 n 假設自由進出 (free entry and free exit). Chapter 8 47

長期均衡產量 Price ($ per unit of output) 長期, 規模擴大, 產量增加到 q 3. 長期利潤 EFGD > 短期的ABCD. LMC LAC SMC D $40 SAC A C G E B P = MR F $30 短期受制於固定要素 在 P = $40 > ATC. 利潤為 ABCD. q 1 q 2 Chapter 8 q 3 Output 48

長期均衡產量 問題: 如果因為產量增加, 價格降到 $30, 廠商仍有利潤嗎? Price ($ per unit of output) LMC LAC SMC D $40 SAC A C G E B P = MR F $30 q 1 q 2 Chapter 8 q 3 Output 49

長期 –進出自由 • 利潤引誘新廠 供給增加一直到利潤為零 $ per unit of output Firm Industry S 1 LMC $40 LAC $30 P 1 S 2 P 2 D q 2 Q 1 Output Chapter 8 Q 2 Output 51

長期的競爭均衡 – 虧損 • 虧損會使廠商退出, 供給減少, 恢復利潤到零 $ per unit of output Firm LMC $ per unit of output LAC $30 P 2 $20 P 1 Industry S 2 S 1 D q 2 Output Chapter 8 Q 2 Q 1 Output 52

長期均衡產量 n 長期競爭均衡 1) MC = MR 2) P = LAC n 沒有進入或退出的動機 n Profit = 0 3) Equilibrium Market Price Chapter 8 53

長期利潤永遠為零 Ticket Price LMC LAC 中型城市的 美式足球隊 門票 =$7 利潤為零 $7 1. 0 Chapter 8 Season Tickets Sales (millions) 57

長期利潤永遠為零 Ticket Price LAC Economic Rent LMC $10 $7 同一隊在大城市 可賣門票到 $10 1. 3 Chapter 8 Season Tickets Sales (millions) 58

成本不變產業 (Constant-Cost Industry) 經濟利潤 新廠加入 $ per unit of output MC AC $ per unit of output P 2 Q 1 增至Q 2 長期供給線 = SL = LRAC. S 1 S 2 C P 2 A P 1 B SL P 1 D 1 q 2 Q 1 Output Chapter 8 Q 2 D 2 Output 61

成本遞增產業 (Increasing-Cost Industry) $ per unit of output SMC 2 SMC 1 LAC 2 LAC 1 P 2 $ per unit of output 產業產量增加, 要素漲價 導至長期均衡價格提高 S 1 S 2 P 3 P 1 P 1 B A D 1 q 2 SL Q 1 Output Chapter 8 Q 2 Q 3 D 1 Output 62

成本遞減產業 (Decreasing-Cost Industry) $ per unit of output 因為要素價格下跌 產業長期均衡價跌 $ per unit of output SMC 1 S 2 SMC 2 LAC 1 P 2 LAC 2 P 1 P 3 A B SL D 1 q 2 Q 1 Q 2 Output Chapter 8 Q 3 D 2 Output 63

對產品課稅, 產業的產量受影響 Price ($ per unit of output) S 2 = S 1 + t S 1 t P 2 S 1 移到 S 2 產量減到 Q 2 價格漲到 P 2. P 1 D Q 2 Q 1 Chapter 8 Output 65

End of Chapter 8 Profit Maximization and Competitive Supply Chapter 8