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Working Paper
Time-Inconsistent Optimal Quantity of Debt
A key property of the Aiyagari-type heterogeneous-agent models is that the equilibrium interest rate of public debt lies below the time discount rate. This fundamental property, however, implies that the Ramsey planner's fiscal policy may be time-inconsistent because the forward-looking planner would have a dominate incentive to issue plenty of debt, such that all households are fully self-insured against idiosyncratic risk whenever the interest rate of government borrowing is lower than the household time discount rate. But such a full self-insurance allocation may be paradoxical because, to ...
Working Paper
Optimal Fiscal Policies under Market Failures
The aggregate capital stock in a nation can be overaccumulated for many different reasons. This paper studies which policy or policy mix is more effective in achieving the socially optimal (modified golden rule) level of aggregate capital stock in an infinite-horizon heterogeneous-agents incomplete-markets economy where capital may be over-accumulated for two distinct reasons: (i) precautionary savings and (ii) production externalities. By solving the Ramsey problem analytically along the entire transitional path, we show that public debt and capital taxation play very distinct roles in ...
Working Paper
The Determination of Public Debt under both Aggregate and Idiosyncratic Uncertainty
We analyze the Ramsey planner's decisions to finance stochastic public expenditures under incomplete insurance markets for idiosyncratic risk. We show analytically that whenever the market interest rate lies below the time discount rate, the Ramsey planner has a dominant incentive to increase debt to meet the private sector's demand for full self-insurance regardless of the relative size of aggregate shocks---suggesting a departure from tax smoothing. However, if a full self-insurance Ramsey allocation is infeasible in the absence of a government debt limit, an interior or bounded Ramsey ...
Working Paper
Implementing the Modified Golden Rule? Optimal Ramsey Capital Taxation with Incomplete Markets Revisited
What is the prescription of Ramsey capital taxation in the long run? Aiyagari (1995) addressed the question in a heterogeneous-agent incomplete-markets (HAIM) economy, showing that a positive capital tax should be imposed to implement the so-called modified golden rule (MGR). This paper revisits the long-standing issue. Working with commonly used separable isoelastic preferences, we show (i) the multiplier on the resource constraint of the Ramsey problem must diverge in the limit if a Ramsey steady state exists, (ii) there is no Ramsey steady state when the elasticity of intertemporal ...
Working Paper
Optimal Fiscal Policies under Market Failures
The aggregate capital stock in a nation can be overaccumulated for many different reasons. This paper studies which policy or policy mix is more effective in achieving the socially optimal (golden rule) level of aggregate capital stock in an infinite-horizon heterogeneous-agents incomplete-markets economy where capital is over-accumulated for two distinct reasons: (i) precautionary savings and (ii) production externalities. By solving the Ramsey problem analytically along the entire transitional path, we show that public debt and capital taxation play very distinct roles in dealing with the ...
Working Paper
The Determination of Public Debt under both Aggregate and Idiosyncratic Uncertainty
We use an analytically tractable, heterogeneous-agent incomplete-markets model to show that the Ramsey planner's decision to finance stochastic public expenditures implies a departure from tax smoothing and an endogenous mean-reverting force to support positive debt growth despite the government's precautionary saving motives. Specifically, the government's attempt to balance the competing incentives between its own precautionary saving (tax smoothing) and households' precautionary saving (individual consumption smoothing)---even at the cost of extra tax distortion---implies an endogenous, ...
Working Paper
Optimal Ramsey Taxation in Heterogeneous Agent Economies with Quasi-Linear Preferences
We build a tractable heterogeneous-agent incomplete-markets model with quasi-linear preferences to address a set of long-standing issues in the optimal Ramsey taxation literature. The tractability of our model enables us to analytically prove the existence of the Ramsey steady state and establish several novel results: (i) The failure of the modified golden rule (MGR) cannot by itself justify a positive steady-state capital tax---we prove that in the absence of wealth-redistribution effects the optimal capital tax is exclusively zero in the Ramsey steady state regardless of the validity of ...
Working Paper
Implementing the Modified Golden Rule? Optimal Ramsey Capital Taxation with Incomplete Markets Revisited
What is the prescription of Ramsey capital taxation in the long run? Aiyagari (1995) addressed the question in a heterogeneous-agent incomplete-markets (HAIM) economy, showing that a positive capital tax should be imposed to implement the so-called modified golden rule (MGR). In deriving the MGR result, Aiyagari (1995) implicitly assumed that the multiplier on the resource constraint of the Ramsey problem converges to a finite positive value in the limit. We first show that this implicit assumption has a strong implication for the shadow price of Ramsey taxation in the limit: it must go to ...
Working Paper
Time-Inconsistent Optimal Quantity of Debt
A key property of the Aiyagari-type heterogeneous-agent models is that the equilibrium interest rate of public debt lies below the time discount rate. This fundamental property, however, implies that the Ramsey planner’s fiscal policy may be time-inconsistent because the forward-looking planner would have a dominant incentive to issue plenty of debt such that all households are fully self-insured against idiosyncratic risk. But such a full self-insurance allocation may be paradoxical because, to achieve it, the optimal labor tax rate may approach 100% and aggregate consumption may approach ...
Working Paper
Are Government Bonds Net Wealth or a Liability? ---Optimal Debt and Taxes in an OLG Model with Uninsurable Income Risk
A positive national debt is often rationalized either by the assumption of dynamic inefficiency in an overlapping-generations (OLG) model, or by the hypothesis of heterogeneous-agents and incomplete-markets (HAIM) in an infinite horizon model. Both assumptions imply insufficient private liquidity to support private saving and investment, thus calling for a positive level of public debt to improve social welfare. However, since public debt is financed often by distortionary future taxes, optimal debt and tax policies ought to be studied jointly in a single framework. In this paper we use a ...