The Macroeconomy
LECTURE 2
Determinants of National Income – Long-Run Foundations
Today’s Topics:
modeling the macroeconomy what determines the economy’s total 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 how equilibrium in the goods market is achieved
Text treatment: Mankiw 8th (& 7th) edition, Ch. 3
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Modeling the Macroeconomy
Key characteristics 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
Equilibrium
goods market loanable funds market
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Figure 3.1 The Circular Flow of Dollars Through the Economy Mankiw: Macroeconomics, Seventh Edition
Copyright © 2010 by Worth Publishers
Factors of production
K = capital: tools, machines, and structures used in production L = labor: the physical and mental efforts of workers
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The production function: 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 exhibits constant returns to scale
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Returns to scale: a review
Initially Y1 = F (K1 , L1 ) Scale all inputs by the same factor z: K2 = zK1 and L2 = zL1
(e.g., if z = 1.2, then all inputs are increased by 20%)
What happens to output, Y2 = F (K2, L2 )? If constant returns to scale, Y2 = zY1 If increasing returns to scale, Y2 > zY1 If decreasing returns to scale, Y2 < zY1
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Assumptions in the production function model
1. Technology is fixed. 2. The economy’s supplies of capital and labor
are fixed at
K K
and
LL
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Determining GDP
Output is determined by the fixed factor supplies and the fixed state of technology:
Y F (K , L)
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The Distribution of National Income:
Market for Factors of Production Distribution of NI is determined by factor prices, the prices per unit firms pay for the factors of production
wage = price of L rental rate = price of K
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Notation
W R P = nominal wage = nominal rental rate = price of output
W /P = real wage (measured in units of output) R /P = real rental rate
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How factor prices are determined
Factor prices are determined by supply and demand in factor markets. Recall: Supply of each factor is fixed.
K, L
What about demand?
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Demand for labor
Assume markets are competitive: each firm takes W, R, and P as given. Basic idea: A firm hires each unit of labor if the cost does not exceed the benefit.
cost = real wage benefit = marginal product of labor
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Marginal product of labor (MPL) definition: The extra output the firm can produce using one additional unit of labor (holding other inputs fixed): MPL = F (K, L +1) – F (K, L)
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MPL and the production function
Y
output
F (K , L )
1
MPL
As more labor is added, MPL
MPL
1
MPL
1
Slope of the production function equals MPL
labor
L
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Diminishing marginal returns
As a factor input is increased, its marginal product falls (other things equal).
Intuition: Suppose L while holding K fixed
fewer machines per worker lower worker productivity
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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
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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
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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.