宏观经济学 第三章 经典

The ratio of labor income to total income in the U.S.
1 Labor’s share of total 0.8 income 0.6 0.4 0.2 0 1960
Labor’s share of income is approximately constant over time. (Hence, capital’s share is, too.)
The production function
denoted Y = F(K, L) shows how much output (Y ) the economy can
produce from K units of capital and L units of labor
reflects the economy’s level of technology
Y
output
MPL
As more labor is added, MPL
F (K , L)
1
MPL
1
MPL
1
Slope of the production function equals MPL
diminishing marginal product
labor
L
Exercise :
Which of these production functions have
A closed economy, market-clearing model Supply side factor markets (supply, demand, price) determination of output/income
Demand side determinants of C, I, and G
2. Determining the rental rate
We have just seen that MPL = W/P. The same logic shows that MPK = R/P :
diminishing returns to capital: MPK as K
The MPK curve is the firm’s demand curve for renting capital. Firms maximize profits by choosing K such that MPK = R/P .
Y MPL L MPK K economic profit
In the real world, firm owners and capital owners
are usually the same people and, therefore, economic profit and the return to capital are often lumped together.
Suppose Y1 = F (K1 , L1 ) Scale all inputs by the same factor z:
K2 = zK1 & L2 = zL1
Y2 = F (K2, L2 )?
K K L L
Y F (K, L)
3.2 The distribution of national income
The distribution of national income is determined by
factor prices.
factor prices the prices per unit
diminishing marginal returns to labor?
a) F (K , L) 2K 15L
b) F (K , L)
KL
c) F (K , L) 2 K 15 L
MPL and the demand for labor
△Profit=△Revenue - △Cost
that firms pay for the factors of production Wage
– price of L
rental rate
– price of K
How a Factor of Production Is Compensated
Since we have assumed that supply is fixed
using an additional unit of labor (holding other inputs fixed):
MPL = F (K, L +1) – F (K, L)
ቤተ መጻሕፍቲ ባይዱ导数形式
MPL dF (K , L) dL
MPL and the production function
How dose it come?
The factor demand curve determines the equilibrium factor
price.
Notation & Assumption
concepts
W = 名义工资（ nominal wage ） R = 名义租金率（ nominal rental rate ） P = 产出的价格（ price of output ） W /P = 实际工资（ real wage which measured in units of goods rather than in dollars R /P = 实际租金（ real rental rate which measured in units of goods ）
Equilibrium goods market loanable funds market
3.1 Factors of production
K = capital: tools, machines, and structures used in production L = labor: the physical and mental efforts of workers
how equilibrium in the goods market is achieved
The Circular Flow of Dollars Through the Economy
>0,budget surplus <0,budget deficit
Outline of model
W L R K
Tips:
F .O.C. 0 L
MPL and the demand for labor
Units of output
Real wage
Each firm hires labor up to the point where MPL = W/P.
MPL, Labor demand Units of labor, L Quantity of labor demanded
CHAPTER
3
Part A
National Income: Where it Comes From and Where it Goes
MACROECONOMICS
N. GREGORY MANKIW
周泳宏 暨南大学 经济学院
In this chapter, you will learn…
what determines the economy’s total

Assumption A competitive firm
Facing a given W, R and P
1. Demand for labor
Marginal Product of Labor (MPL ) The extra output the firm can produce
How income is distributed:
W L total labor income = P R K total capital income = P
MPL L
MPK K
If production function has constant returns to scale, then
output/income
how the prices of the factors of production are
determined
how total income is distributed
what determines the demand for goods and
services
实际租金的可能影响 假设香港政府在实施“输入内 地专才计划”中，放宽内地 “资讯科技及财经服务方面专 门人才”认定条件并简化申请 程序。 假设香港政府在实施“输入内 地专才计划”中，确实引入了 大批香港稀缺人才。 的人才？
进一步的思考：你要成为什么样
Appendix： Returns to scale
= P×MPL- W
equilibrium： P×MPL= W MPL= W/P
marginal product of labor equals the real wage.
Exercise
Prove
Max MPL W P
Max (Profit)
P F (K , L)
K
MPK, demand for capital Units of capital, K
The Neoclassical Theory of Distribution
states that each factor input is paid its marginal
product
is accepted by most economists
accounting profit MPK K economic profit
let
If economic profit is zero, the “profit” in the
national income accounts must be mostly the return to capital.
The equilibrium real wage
Units of output Labor supply
The real wage adjusts to equate labor demand with supply.
equilibrium real wage
L
MPL, Labor demand Units of labor, L
1970
1980
1990
2000
☆ The ratio of labor income to total
income in Chinese Provinces: 2009
中国统计年鉴2010，劳动者报酬÷ 地区生产总值，当年价
Discussion
在Y = F(K, L)中，影响L？ 影响F？
以下事件对香港实际工资和资本
Y MPL L MPK K economic profit
national income
labor income
capital income
constant returns to scale, profit maximization, and competition together imply that economic profit is zero.
The equilibrium real rental rate
Units of output Supply of capital
The real rental rate adjusts to equate demand for capital with supply.
equilibrium R/P
exhibits constant returns to scale
Determining output
we assume that the supplies of capital and labor and
the technology are fixed, output is also fixed