## Interest Rate Defenses of Currency Pegs

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### Abstract and Main Thesis
- Paper: WP/04/85 (May 2004).
- Author: Juan Solé; Authorized for distribution by Donald J. Mathieson.
- JEL Classification Numbers: E58, F31, F41.
- Keywords: Interest rates, exchange rates, currency crises.
- Main finding: Raising short-term interest rates can defend a currency peg by stemming demand for foreign reserves, provided a specific asset-market friction is present.
- Key mechanism emphasized: money is required for asset transactions (the friction emphasized is the same as in Lucas (1990): money is required for asset transactions).
- Central implication: an interest rate defense can always be successful, but at great costs for domestic agents; hence governments are reluctant to sustain the policy for long periods.

### Model Setup and Frictions
- Framework: general equilibrium model with asset market frictions.
- Friction specified: cash-in-advance or money-required-for-asset-transactions friction (as in Lucas (1990); Lucas and Stokey (1987) referenced).
- Timing and structure: the paper provides a detailed timing diagram (Figure 1: Timing of the Model) and formal derivations (Appendix I–III).
- Behavioral mechanism:
  - When the government raises domestic interest rates, agents want to increase holdings of domestic currency.
  - Increased domestic-currency holdings enable acquisition of more domestic-currency-denominated assets.
  - As a result, agents do not run on central bank reserves; the peg can survive.

### Analytical Results (Structure and Findings)
- Comparative policy analysis: the paper derives equilibrium under two defense policies:
  - Reserves policy (equilibrium analyzed in Section III.A; Table 1: Reserves Policy).
  - Interest-rate policy (equilibrium analyzed in Section III.B; Table 2: Interest-Rate Policy).
- Existence and success of interest-rate defense:
  - Proposition: interest-rate defense can be effective in preventing runs on reserves given the liquidity friction.
  - Lemma and proofs: technical results supporting equilibria are proved in Appendix I and Appendix II.
- Welfare comparison:
  - The model compares welfare across policies (Section III.C; Table 3: Bond Prices; Figure 4: Utility Levels for Domestic Agents; Figure 5: Consumption of Domestic Goods by Domestic Agents).
  - Finding: while interest-rate defenses can preserve the peg, they impose significant welfare costs on domestic agents relative to alternative policies.

### Quantitative and Numerical Analysis
- Numerical results and illustrations are provided in Appendix IV and Figures:
  - Figure 2: Household’s Payoffs During Crisis.
  - Figure 3: Bond Prices.
  - Figure 6: Bond Prices Under Interest-Rate Policy.
  - Figure 7: Utility for π = 0.7.
- Tables and figures used to illustrate:
  - Table 1: Reserves Policy.
  - Table 2: Interest-Rate Policy.
  - Table 3: Bond Prices.
  - Table 4: Change in Domestic Consumption of Domestic Good.

### Policy Implications and Interpretation
- Rationale for historic policy choice:
  - Interest-rate hikes are commonly used to defend pegs because they reduce demand for foreign reserves via the liquidity channel present in this model.
- Practical constraint:
  - Although always potentially successful in the model, the high costs borne by domestic agents explain governments’ reluctance to sustain high interest rates for long periods.
- Relation to literature:
  - The friction and mechanism connect to Lucas (1990) and to literature on liquidity constraints and crises (e.g., Krugman (1979); Obstfeld (1986); Grilli and Roubini (1992)).
  - The paper situates its contribution relative to other works on interest-rate defenses and crises (e.g., Drazen 2000, Flood and Jeanne 2003, Lahiri and Végh 2003).

### Conclusions
- Summary statement: Interest-rate defenses can stop reserve runs in the presence of a money-for-asset-transactions friction, but such defenses impose large welfare costs on domestic agents, limiting their practical use over extended periods.
- Research contribution: provides a general equilibrium formalization of a policy widely observed in practice and absent from many monetary models.

*Source: IMF Working Paper WP/04/85, "Interest Rate Defenses of Currency Pegs" by Juan Solé (May 2004).*

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