成本分析
第7章
1
成本的经济分析
2
短期
• The short run: The period in which firms
can adjust production only by changing
variable factors such as materials and
labor but cannot change fixed factors
such as capital.
3
固定成本
• The cost related to fixed factors is called
fixed cost (固定成本，不变成本).
• A firm’s fixed costs, sometimes called
“overhead” (企业一般管理费用) or
“sunk costs” (沉入成本), must be paid
even if the firm produces no output, and
they will not change if output changes.
4
变动成本
• The cost related to variable factors is
called variable cost (变动成本，可变成本
).
• Variable costs are those which vary as
output changes. By definition, VC begins
at zero when q is zero.
5
总成本是可达到的最小成本
• Total cost represents the lowest total
dollar expense needed to produce each
level of output q.
• 说明：与生产函数的处理类似，总成本
也是指给定产量时的最小成本，目的是
为了让函数关系具有唯一性。
6
Total
cost
in short run:
in long run: Total
cost
Variable
cost=
Fixed
cost
Variable
cost
+
7
(1) (2) (3) (4)
Quantity Fixed cost Variable cost Total cost
=(2)+(3)
q FC($) VC($) TC($)
0 55 0 55
1 55 30 85
2 55 55 110
3 55 75 130
4 55 105 160
5 55 155 210
6 55 225 280
8
边际成本
• The concept of marginal cost is one of the
most essential in microeconomics.
• Marginal cost (MC) denotes the extra or
additional cost of producing 1 extra unit
of output.
9
For an airline flying planes
with empty seats, the added
cost of another passenger is
quite low.
But on a hot summer day,
when everyone’s
conditioners are running,
the added electric power
comes at a high marginal
cost.
10
边际成本的计算
(1) (2) (3)
Output Total cost Marginal cost
Q TC($) MC($)
0 55
1 85
2 110
3 130
4 160
5 210
30
25
20
30
50
11
利用变动成本计算边际成本
(1) (2) (3)
Output Variable cost Marginal cost
Q VC($) MC($)
0 0
1 30
2 55
3 75
4 105
5 155
30
25
20
30
50
12
MC = TCq+1－ TCq
= (VCq+1＋FC) － (VCq＋FC)
= VCq+1 － VCq
数学推导
• 为什么可以用变动成本来计算边际成本：
13
总成本和边际成本的关系
Output
T
ot
al
c
os
t
Output
M
ar
gi
na
l c
os
t
14
平均成本
Average cost
(or unit cost) =
total cost
output =
TC
q =
AC
Average
fixed cost =
fixed cost
output =
FC
q = AFC
Average
variable cost
=
variable cost
output
=
VC
q = AVC
15
总成本、固定成本和变动成本
Total cost
Variable cost
Fixed cost
Quantity
C
os
t
16
平均成本和边际成本
Quantity
A
ve
ra
ge
a
nd
m
ar
gi
na
l c
os
t MC
AC
AVC
AFC
平均成本最小
平均变动成本最小
17
平均成本与边际成本的关系
成本
产量
边际成本
平均成本
平均成本最低点
边际成本曲
线自下而上
穿越平均成
本曲线的最
低点。
18
平均成本>边际成本
成本
产量
边际成本
平均成本
边际成本＜
平均成本,
平均成本随
着产量增加
而向下。
16元
22
12元
19
平均成本<边际成本
成本
产量
边际成本
平均成本
17元
边际成本＞
平均成本,
平均成本随
着产量增加
而向上。
23元
50 20
边际成本和平均成本的关系
ACq+1 =
ACq×q＋MC
q＋1
=
ACq×(q＋1) ＋MC－ACq
q＋1
= ACq＋
MC－ACq
q＋1
21
小结
•• If MC>AC, then AC is rising.
•• If MC=AC, then AC is at its low point.
•• If MC<AC, then AC is falling.
Quantity
A
C
a
nd
M
C
= ACq＋
MC－ACq
q＋1
ACq+1
AC
22
边际成本和平均变动成本的关系
AVCq+1=
AVCq×q＋MC
q＋1
=
AVCq×(q＋1) ＋MC－AVCq
q＋1
= AVCq＋
MC－AVCq
q＋1
23
小结
•• If MC>AVC, then AVC is rising.
•• If MC=AVC, then AVC is at its low point.
•• If MC<AVC, then AVC is falling.
Quantity
A
C
a
nd
M
C
= AVCq＋
MC－AVCq
q＋1
AVCq+1
AVC
24
斜率和边际成本的关系
Tangent line
Total cost curve
1 unit of output
Marginal
costa
25
产量与成本之间的联系
• The cost curve for a firm depends very
closely on ① the prices of inputs and ②
the firm’s production function.
• If you know factor prices and the
production function, you can calculate
the cost curve.
26
(1) (2) (3) (4) (5) (6)
Output Land Labor Rent Wage Total cost
(tons) (acres) (workers
)
($/acre
)
($/worker
)
($)
0 10 0 5 55
1 10 6 5 ?
2 10 11 5 110
3 10 15 5 130
4 10 21 5 160
5 10 31 5 ?
6 10 45 5 280
7 10 63 5 370
8 10 85 5 480
85
210
27
报酬递减和U形成本曲线
Labor
M
ar
gi
na
l p
ro
du
ct
o
f l
ab
or
M
ar
gi
na
l c
os
t
Output
A
B
D
A
B
D
MC
AC
In the short run:
28
最小成本规则
To a given output:
Marginal product of input A
Price of input A
=
Marginal product of input B
Price of input B
= ……
29
等边际原理
This gives you the marginal
product per dollar of output.
30
替代规则
• If the price of one factor falls while all
other factor prices remain the same,
firms will profit by substituting the now-
cheaper factor for all the other factors.
MP of Labor
Price of Labor
=
MP of Capital
Price of Capital
31
背景知识
• 在资本主义由工场手工业向大机器生产过
渡的历史时期，由于机器操作的简单性，
女工、童工加入劳动行列，劳动供给增加。
与此同时，大机器生产要求相对较多的资
本，资本的供给相对稀缺。这是导致工人
当时生活贫困的主要原因。
• 当资本不断积累，而生产又要求较为复杂
的劳动技能时，在要素市场上，资本不可
能总是处于有利的竞争地位。
32
短期成本与长期成本的关系
成本
产量
长期平均成本
1 亩地 2 亩地 4 亩地3 亩地
1 亩地
更有利
2 亩地
更有利
3 亩地
更有利
4 亩地
更有利
33
规模经济与规模不经济
成本
产量
长期平均成本
规模经济 规模不经济
34
经济成本和企业会计
35
经济成本和会计成本
• 经济成本（economic cost）：投入生产
的所有资源的机会成本。
• 会计成本（accounting cost）：按照会计
规则计算的成本
• 在会计帐面上显示出来的经济成本称为
外显（显性）成本（explicit costs），在
会计帐面上不能显示出来的经济成本称
为内含（隐性）成本（implicit costs）。
36
经济利润
• 经济成本 = 外显成本 + 内含成本
= 机会成本
• 经济利润 = 销售收入 – 经济成本
• 经济利润是计入了所有使用的资源代价
后的纯收益。
37
一个体饭馆业主使用自己的
店面， 1年盈利3万元，这个
3万元称之为会计利润。
若不开饭馆，在所有可选工作中
最高可赚得2万元，人力的经济成
本就是2万元。如果店面用于出租
可以获得万元租金，那么店面
的经济成本就是 万元。
考虑到经济成本后，这个个体饭馆业主的经
济利润为－ 万元。
38
收益表
(1) Net sales $250,000
Less cost of goods sold:
(2) Materials $50,000
(3) Labor cost 90,000
(4) Miscellaneous operating costs 10,000
(5) Less overhead costs:
(6) Selling and administrative costs 15,000
(7) Rent for building 5,000
(8) Depreciation 15,000
(9) Operating expenses $185,000 185,000
(10
)
Net operating income $65,000
39
收益表
(10
)
Net operating income $65,000
Less:
(11
)
interest charges on equipment loan 6,000
(12
)
State and local taxes 4,000
(13
)
Net income before income taxes $55,000
(14
)
Less: Corporation income taxes 18,000
(15
)
Net income (or profit) after taxes $37,000
(16
)
Less: Dividends paid on common stock 15,000
(17
)
Addition or retained earnings $22,000
40
The depreciation is taken in
annual accounting charges over
the asset’s accounting lifetime
折旧
$1
0,
00
0
$1
0,
00
0
$1
0,
00
0
$1
0,
00
0
$1
0,
00
0
$1
0,
00
0
$1
0,
00
0
$1
0,
00
0
$1
0,
00
0
$1
0,
00
0
∑depreciation =
the capital good’s
historical cost or
purchase price.
Depreciation = the
annual cost of a capital
input that a company
actually owns itself.
41
资产负债表
Assets Liabilities and net worth
Liabilities
Current assets: Current liabilities:
Cash $20,000 Accounts payable $20,000
Inventory 80,000 Notes payable 30,000
Fixed assets: Long-term liabilities:
Equipment 150,000 Bonds payable 100,000
Buildings 100,000
Net worth
Stockholders’ equity:
________ Common stock 200,000
Total $350,000 Total $350,00042
关于资产负债表
• The income statement measures the flows
into and out of the firm, while the
balance sheet measures the stocks of
assets and liabilities at the end of the
accounting year.
• A balance sheet must always balance:
Total assets = total liabilities + net worth
43
例子
• Suppose total assets are down $40,000;
liabilities remain unchanged. This means
total net worth has decreased by $40,000,
and should write net worth down from
the previous $200,000 to only $160,000.
Assets Liabilities and net worth
Liabilities
$40,000 Net worth
Common stock $40,000
44
会计惯例
• The value placed on almost every
item reflects its historical costs.
45
说明
• “收入表”是描述一指定会计时间段中
货币流入和流出企业的情况。
• “资产负债表”是指在某一特定的会计
时刻，企业的资产、负债和所有者权益
状况。
• 总之，“收入表”是对一时段而言的，
“资产负债表”是对一时点而言的。
46
机会成本
47
机会成本
•• The opportunity cost (机会成本) is the
value of the good and service forgone (放
弃).
•• The opportunity cost includes all
consequences (结果), whether they
reflect explicit monetary transactions (货
币交易) or not.
48
The immediate dollar cost The immediate dollar cost
of going to a movie of going to a movie
instead of reading your instead of reading your
economics textbook is the economics textbook is the
price of the movie of the movie ticket.
The opportunity cost also includes The opportunity cost also includes
the possibility of gaining a better the possibility of gaining a better
understanding of microeconomics understanding of microeconomics
and therefore becoming more and therefore becoming more
successful in in business.
49
问题
•• Why do the students watch more TV the
week after exams than the week before
exams?
50
市场价格与机会成本
•• 在一个良好运行的市场上，价格等于机
会成本。
$ (Market price)
$ (Opportunity cost)
$
51
生产、成本理论和企业决策
附录
52
生产函数的数值例子
Q=100 2LA
Q = output;
L = labor;
A = land.
The production function is a
constant-returns-to-scale
production function, a special
case of the Cobb-Douglas
production function.
53
346 490 600 692 775 846
316 448 548 632 705 775
282 400 490 564 632 692
245 346 423 490 548 600
200 282 346 400 448 490
141 200 245 282 316 346
6
5
4
3
2
1
0 1 2 3 4 5 6
Constant
returns to
scale
Labor
L
an
d
54
346 490 600 692 775 846
316 448 548 632 705 775
282 400 490 564 632 692
245 346 423 490 548 600
200 282 346 400 448 490
141 200 245 282 316 346
6
5
4
3
2
1
0 1 2 3 4 5 6
Diminishing
marginal
product of
labor
Labor
L
an
d
82 64 54 48 42
55
346 490 600 692 775 846
316 448 548 632 705 775
282 400 490 564 632 692
245 346 423 490 548 600
200 282 346 400 448 490
141 200 245 282 316 346
6
5
4
3
2
1
0 1 2 3 4 5 6
Diminishing marginal product of land
Labor
L
an
d
52
58
67
77
101
56
给定产量的最低要素成本组合
(1) (2) (3) (4)
Input Combination Total cost Total cost
Labor Land PL=$2 PL=$2
L A PA=$3 PA=$1
A 1 6 20 ?
B 2 3 13 ?
C 3 2 12 ?
D 6 1 15 ?
57
给定产量的最低要素成本组合
(1) (2) (3) (4)
Input Combination Total cost Total cost
Labor Land PL=$2 PL=$2
L A PA=$3 PA=$1
A 1 6 20 8
B 2 3 13 7
C 3 2 12 8
D 6 1 15 13
58
等产量曲线
346 490 600 692 775 846
316 448 548 632 705 775
282 400 490 564 632 692
245 346 423 490 548 600
200 282 346 400 448 490
141 200 245 282 316 346
6
5
4
3
2
1
0 1 2 3 4 5 6
Labor
L
an
d
59
6
5
4
3
2
1
L
an
d
0 1 2 3 4 5 6
Labor
A
B
C
D
q
Equal-product
curve or isoquant
There are an infinite
number of equal-
product contour
lines (等值线) in the
map.
60
6
5
4
3
2
1
L
an
d
0 1 2 3 4 5 6
Labor
A
B
D
q
C
△A
△L
M
△A
C
△L
N
M→N: △A×MPA=△L ×MPL
替代率
61
等成本线
6
5
4
3
2
1
L
an
d
0 1 2 3 4 5 6 7 8
Labor
Labor price = $2, Land price = $3
TC=$3
TC=$6
TC=$9
TC=$12
TC=$15
TC=$18
equal-cost Line:
62
6
5
4
3
2
1
L
an
d
0 1 2 3 4 5 6 7 8
Labor
TC=$3
TC=$6
TC=$9
TC=$12
TC=$15
equal-cost Line:
△A
△L
△A×PA=
△L ×PL
替代率
63
最低成本投入组合
6
5
4
3
2
1
L
an
d
0 1 2 3 4 5 6 7 8
Labor
TC=$3
TC=$6
TC=$9
TC=$12
A
B
C
D
64
最低成本条件
65
说明
• 等产量线方法一般用于企业的长期行为
分析，因为对于长期来说，所有的生产
要素都可以改变，所以可以在等产量线
上进行选择。
• 对于短期分析而言，按惯例一般不使用
等产量线分析方法。
66
End Of Lesson
67
