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Working Paper
Are Government Bonds Net Wealth or a Liability? ---Optimal Debt and Taxes in an OLG Model with Uninsurable Income Risk
The rapidly growing national debt in the U.S. since the 1970s has alarmed and intrigued the academic world. Consequently, the concept of dynamic (in)efficiency in an overlapping generations (OLG) world and the importance of the heterogeneous-agents and incomplete markets (HAIM) hypothesis to justify a high debt-to-GDP ratio have been extensively studied. Two important consensus emerge from this literature: (i) The optimal quantity of public debt is positive—due to insufficient private liquidity to support private saving and investment (see, e.g., Barro (1974), Woodford (1990), and Aiyagari ...
Working Paper
The Determination of Public Debt under both Aggregate and Idiosyncratic Uncertainty
We use an analytically tractable model to show that the Ramsey planner's decisions to finance stochastic public expenditures under uninsurable idiosyncratic risk implies a departure from tax smoothing. In the absence of state-contingent bonds the government's attempt to balance the competing incentives between tax smoothing and individual consumption smoothing---even at the cost of extra tax distortion---implies a bounded stochastic unit root component in optimal taxes. Nonetheless, a sufficiently high average level of public debt to support individuals’ self-insurance position is welfare ...
Working Paper
Are Unconditional Lump-sum Transfers a Good Idea?
The role of unconditional lump-sum transfers in improving social welfare in heterogenous agent models has not been thoroughly understood in the literature. We adopt an analytically tractable Aiyagari-type model to study the distinctive role of unconditional lump-sum transfers in reducing consumption inequality due to ex-post uninsurable income risk. Our results show that in the presence of ex-post heterogeneity and in the absence of wealth inequality, unconditional lump-sum transfers are not a desirable tool for reducing consumption inequality—the Ramsey planner opts to rely solely on ...
Working Paper
The Determination of Public Debt under both Aggregate and Idiosyncratic Uncertainty
We use an analytically tractable model to show that the Ramsey planner's decisions to finance stochastic public expenditures under uninsurable idiosyncratic risk implies a departure from tax smoothing. In the absence of state-contingent bonds the government's attempt to balance the competing incentives between tax smoothing and individual consumption smoothing---even at the cost of extra tax distortion---implies a bounded stochastic unit root component in optimal taxes. Nonetheless, a sufficiently high average level of public debt to support individuals’ self-insurance position is welfare ...
Working Paper
The Ramsey Steady-State Conundrum in Heterogeneous-Agent Economies
In infinite horizon, heterogeneous-agent and incomplete-market models, the existence of an interior Ramsey steady state is often assumed instead of proven. This paper makes two fundamental contributions: (i) We prove that the interior Ramsey steady state assumed by Aiyagari (1995) does not exist in the standard Aiyagari model. Specifically, a steady state featuring the modified golden rule and a positive capital tax is feasible but not optimal. (ii) We design a modified, analytically tractable version of the standard Aiyagari model to unveil the necessary and/or sufficient conditions for the ...
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
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
Should Capital Be Taxed?
We design an infinite-horizon heterogeneous-agents and incomplete-markets model to demonstrate analytically that in the absence of any redistributional effects of government policies, optimal capital tax is zero despite capital overaccumulation under precautionary savings and borrowing constraints. Our result indicates that public debt is a better tool than capital taxation to restore aggregate productive efficiency.
Working Paper
Why Might Lump-sum Transfers Not Be a Good Idea?
We adopt an analytically tractable Aiyagari-type model to study the distinctive roles of unconditional lump-sum transfers and public debt in reducing consumption inequality due to uninsurable income risk. We show that in the absence of wealth inequality, using lump-sum transfers is not an optimal policy for reducing consumption inequality---because the Ramsey planner opts to rely solely on public debt to mitigate income risk without the need for lump-sum transfers. This result is surprising in light of the popularity of universal basic income advocated by many politicians and scholars.
Working Paper
The Ramsey Steady-State Conundrum in Heterogeneous-Agent Economies
In infinite horizon, heterogeneous-agent and incomplete-market models, the existence of an interior Ramsey steady state is often assumed instead of proven. This paper makes two fundamental contributions: (i) We prove that the interior Ramsey steady state assumed by Aiyagari (1995) does not exist in the standard Aiyagari model. Specifically, a steady state featuring the modified golden rule and a positive capital tax is feasible but not optimal. (ii) We design a modified, analytically tractable version of the standard Aiyagari model to unveil the necessary and/or sufficient conditions for the ...