第14章 竞争市场上的企业

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数量
这个图表示出了边际成本曲线MC、平均成本曲线ATC和平均可变成本曲线AVC。它还表示出了市场价格P， 对一个竞争企业而言，市场价格P等于边际收益MR和平均收益AR。在产量为Q1时，边际收益MR1大于边 际成本MC1，因此增加产量增加了利润。在产量为Q2时，边际成本MC2大于边际收益MR2，因此减少产 量增加了利润。利润最大化的产量Qmax是在水平价格线与边际成本曲线相交之处。
• 总收益, TR = P ˣ Q • 平均收益 AR = TR / Q=P • 边际收益 MR = ∆TR / ∆Q
• 对于竞争企业：MR = P
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利润最大化
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什么是竞争市场
• 竞争市场(完全竞争市场)
数量
价格和平均总成本之间阴影方框的面积代表企业的利润。这个方框的高是价格减平均总 成本（P-ATC），而方框的宽是产量Q。在(a)幅中，价格高于平均总成本，因此，企业 有正利润。在(b)幅中，价格低于平均总成本，因此，企业有亏损。
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利润最大化: 数字实例
表2
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Leabharlann Baidu
竞争企业的利润最大化
图1
Costs and 收益
The firm maximizes 利润 by producing the 数量 at which marginal cost equals marginal 收益.
MC2 P=MR1=MR2
MC1
MC ATC P=AR=MR
AVC
0
Q1
QMAX
Q2
利润最大化
• 企业的长期决策
– 退出市场，如果
• 总收益 < 总成本（TR < TC）; • 或者，P < ATC • 或者，利润<0
– 进入市场，如果。。。
• 竞争企业的长期供给曲线
– 边际成本曲线高于平均总成本曲线的部分
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图5
用价格与平均总成本之间面积表示的利润
Price
(a) A firm with 利润s
MC
Price
(b) A firm with 损失es
MC
利润 P ATC
ATC
P=AR=MR ATC P
损失
ATC P=AR=MR
0
Q
数量
0
Q
(利润-maximizing 数量)
(损失-minimizing 数量)
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•2。P=ATC, π=0
• P<ATC, π<0，比较：
• 不生产，则利润＝ - FC
• 生产q* ，则利润＝PQ- TC
•
＝PQ-VC-FC
•
＝Q(P- AVC)-FC
•3.AVC<P<ATC,
•4.P=AVC
•5.P<AVC
沉没成本
– 已经发生且无法收回的成本 – 决策时应该被忽略 – “过去的就让它过去吧” – “覆水难收” – 短期中固定成本是沉没成本
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表1
竞争企业的总收益、平均收益和边际收益
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1. In the 长期, the firm produces on the MC曲线若
P>ATC,...
MC ATC
2. ...but exits 若
P<ATC
0
数量
在长期中，竞争企业的供给曲线是其边际成本MC位于平均总成本曲线ATC以上的部分。 若果价格低于平均总成本，企业退出市场会好一些。
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图3
竞争企业的短期供给曲线
Costs
1. In the 短期, the firm produces on the MC曲线 若P>AVC,...
2. ...but shuts down 若P<AVC.
MC ATC AVC
0
数量
在短期中，竞争企业的供给曲线是平均可变成本曲线AVC以上的边际成本曲线MC部分。 如果价格低于平均可变成本，企业暂时停止营业更好。
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什么是竞争市场
• 企业努力使利润最大化 • 利润=总收益减总成本
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竞争性企业短期利润的5种情况
•1。P>ATC，π>0
短期的市场供给曲线
图6
(a) Individual firm supply
Price
MC
Price
$2.00 1.00
$2.00 1.00
(b) 市场供给 Supply
0
100 200 数量
(firm)
0 100,000 200,000 数量 (market)
在短期中，市场上企业的数量是固定的。因此，(b)幅所示的市场供给曲线，反映了(a) 幅所示的单个企业的边际成本曲线。在这个有1000家企业市场上，市场供给量是1000 乘以每个企业的供给量。
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图4
竞争企业的长期供给曲线
Costs
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竞争市场上的企业
PowerPoint Slides prepared by: Andreea CHIRITESCU Eastern Illinois University
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– 1.市场中有许多买者和卖者 – 2.交易相同产品 – 每个买者和卖者都是价格接受者 – 3.企业自由进出市场
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