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How Central Banks Shape the Economyby@keynesian
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How Central Banks Shape the Economy

by Keynesian TechnologyDecember 8th, 2024
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This section proves Theorem 2(ii) and Proposition 15, analyzing the behavior of ∆ in relation to inflation dynamics. The proof explores the limiting behavior of derivatives and discusses the sharpness of parameter conditions in economic models.
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Author:

(1) David Staines.

Abstract

1 Introduction

2 Mathematical Arguments

3 Outline and Preview

4 Calvo Framework and 4.1 Household’s Problem

4.2 Preferences

4.3 Household Equilibrium Conditions

4.4 Price-Setting Problem

4.5 Nominal Equilibrium Conditions

4.6 Real Equilibrium Conditions and 4.7 Shocks

4.8 Recursive Equilibrium

5 Existing Solutions

5.1 Singular Phillips Curve

5.2 Persistence and Policy Puzzles

5.3 Two Comparison Models

5.4 Lucas Critique

6 Stochastic Equilibrium and 6.1 Ergodic Theory and Random Dynamical Systems

6.2 Equilibrium Construction

6.3 Literature Comparison

6.4 Equilibrium Analysis

7 General Linearized Phillips Curve

7.1 Slope Coefficients

7.2 Error Coefficients

8 Existence Results and 8.1 Main Results

8.2 Key Proofs

8.3 Discussion

9 Bifurcation Analysis

9.1 Analytic Aspects

9.2 Algebraic Aspects (I) Singularities and Covers

9.3 Algebraic Aspects (II) Homology

9.4 Algebraic Aspects (III) Schemes

9.5 Wider Economic Interpretations

10 Econometric and Theoretical Implications and 10.1 Identification and Trade-offs

10.2 Econometric Duality

10.3 Coefficient Properties

10.4 Microeconomic Interpretation

11 Policy Rule

12 Conclusions and References


Appendices

A Proof of Theorem 2 and A.1 Proof of Part (i)

A.2 Behaviour of ∆

A.3 Proof Part (iii)

B Proofs from Section 4 and B.1 Individual Product Demand (4.2)

B.2 Flexible Price Equilibrium and ZINSS (4.4)

B.3 Price Dispersion (4.5)

B.4 Cost Minimization (4.6) and (10.4)

B.5 Consolidation (4.8)

C Proofs from Section 5, and C.1 Puzzles, Policy and Persistence

C.2 Extending No Persistence

D Stochastic Equilibrium and D.1 Non-Stochastic Equilibrium

D.2 Profits and Long-Run Growth

E Slopes and Eigenvalues and E.1 Slope Coefficients

E.2 Linearized DSGE Solution

E.3 Eigenvalue Conditions

E.4 Rouche’s Theorem Conditions

F Abstract Algebra and F.1 Homology Groups

F.2 Basic Categories

F.3 De Rham Cohomology

F.4 Marginal Costs and Inflation

G Further Keynesian Models and G.1 Taylor Pricing

G.2 Calvo Wage Phillips Curve

G.3 Unconventional Policy Settings

H Empirical Robustness and H.1 Parameter Selection

H.2 Phillips Curve

I Additional Evidence and I.1 Other Structural Parameters

I.2 Lucas Critique

I.3 Trend Inflation Volatility

A.2 Behaviour of ∆

The following theorem accomplishes the proof of Theorem 2(ii) and Proposition 15.



To prove existence of the bounds examine the limiting behavior of the derivatives around the poles. At the positive pole






where the first term comes from the first and fourth terms of the previous expression, the second comes from combining terms two, three and six whilst the final term is term five. By taking the non-stochastic limit of the first derivative (187)



it is clear that sgn(d∆/dπ) = sgn(π). As the first derivative is (strictly) positive for (strictly) positive inflation, we know that is strictly convex for non-negative inflation.



Hence



Finally, turning to the sharpness of the parameter condition required by Theorem 2, consider the limit case where



suppose further that



so the distribution of A approaches a two point discrete distribution. The persistent limit means we can transfer this to the distribution of inflation



Furthermore let the upper bound of the shock be arbitrarily increased



so by taking the non-stochastic limit of the steady state (detailed in Appendix D) it is clear that



whilst the probability is scaled down to preserve the boundedness of the expectation by



This paper is available on arxiv under CC 4.0 license.