What role do self-fulfilling expectations play in causing a liquidity trap?

✓ Accepted answer

Self-fulfilling expectations play a critical role in causing a liquidity trap by creating multiple equilibria where arbitrary shifts in inflation expectations render standard monetary policy ineffective.

• Uniqueness of Equilibrium: Research by Benhabib, Uribe, and Schmitt-Grohe demonstrates that when the zero lower bound on nominal interest rates is considered, the economy can suffer from indeterminacy. This means that without a specific policy constraint, expectations can diverge from the central bank's target, leading to arbitrary revisions in inflation paths.
• Failure of Taylor Rules: Standard Taylor-type interest-rate rules may fail to stabilize the economy if agents' expectations of future inflation deviate from the rational forecast. These self-fulfilling dynamics can lead to undesirable equilibria where output and prices become unstable despite active monetary policy.
• Policy Limitations: As highlighted in work by Buiter and Panigirtzoglou, once the economy is in a liquidity trap, conventional tools are limited because lower short-term nominal interest rates cannot be effectively reduced further. This forces a reliance on forward guidance or fiscal coordination to manage expectations.
• Prevention Strategies: To avoid such traps, central banks in the US and UK must ensure that their policy frameworks provide a unique, stable equilibrium. This often involves explicitly committing to achieving a positive inflation target over a longer horizon, thereby anchoring expectations and preventing the self-fulfilling decay of confidence.

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