Math Problem Statement

In a country, output is produced with labor and physical capital. The production function in per-worker terms is y =𝑘^(1/2). The depreciation rate is 2%. The investment rate (γ) is determined as follows:

γ = 0.20 if y < 10

γ = 0.40 if y > 10

Draw a diagram showing the steady state(s) of this model. Calculate the values of any steady state levels of k and y. Also, indicate on the diagram and describe briefly in words how the levels of y and k behave outside of the steady state. Comment briefly on the stability of the steady state(s). Draw a Solow growth graph with all the values afterwards.

Solution

The graph above illustrates the Solow growth model for the given production function, investment rates, and depreciation. Key features:

  1. Production Function (Blue Curve): This represents y=k1/2y = k^{1/2}, showing how output per worker increases with capital per worker.
  2. Investment Curves (Green and Orange):
    • The green dashed line represents investment when γ=0.20\gamma = 0.20, relevant when y<10y < 10.
    • The orange dashed line represents investment when γ=0.40\gamma = 0.40, applicable when y>10y > 10.
  3. Depreciation Line (Red): This is the linear function δk\delta k, showing the constant depreciation rate of 2%.

The two steady states are marked:

  • First steady state at k=100k = 100, where output per worker y=10y = 10, and investment with γ=0.20\gamma = 0.20 intersects depreciation. This point is unstable.
  • Second steady state at k=400k = 400, where output per worker y=20y = 20, and investment with γ=0.40\gamma = 0.40 intersects depreciation. This point is stable.

Summary of Behavior:

  • Below k=100k = 100, capital accumulates, pushing the economy toward the unstable steady state.
  • Between k=100k = 100 and k=400k = 400, capital accumulates due to the higher investment rate, moving the economy to the stable steady state.
  • Above k=400k = 400, capital depreciates, bringing the economy back to the stable point.

Would you like any further details or explanations?


5 Related Questions:

  1. How does a change in the depreciation rate affect the steady states?
  2. What happens if the investment rate does not increase after y=10y = 10?
  3. How would population growth impact the steady-state values?
  4. Can we derive a long-term growth rate in this model?
  5. What happens to output when technological progress is added?

Tip: In the Solow model, a higher investment rate leads to a higher steady-state capital level, but diminishing returns to capital still hold.

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Math Problem Analysis

Mathematical Concepts

Economic Growth Models
Solow Growth Model
Differential Equations
Stability Analysis

Formulas

Production function: y = k^(1/2)
Depreciation function: δk
Investment function: γy

Theorems

Solow Growth Model
Stability of Equilibrium

Suitable Grade Level

Undergraduate Economics or Advanced High School Economics