Dealing with a liquidity trap when government debt matters: Optimal time-consistent monetary and fiscal policy

How does the need to preserve government debt sustainability affect the optimal monetary and fiscal policy response to a liquidity trap? To provide an answer, we employ a small stochastic New Keynesian model with a zero bound on nominal interest rates and characterize optimal time-consistent stabilization policies. We focus on two policy tools, the short-term nominal interest rate and debt-financed government spending. The optimal policy response to a liquidity trap critically depends on the prevailing debt burden. While the optimal amount of government spending is decreasing in the level of outstanding government debt, future monetary policy is becoming more accommodative, triggering a change in private sector expectations that helps to dampen the fall in output and inflation at the outset of the liquidity trap.     

Computing equilibria in dynamic models with occasionally binding constraints

We propose a method to compute equilibria in dynamic models with several continuous state variables and occasionally binding constraints. These constraints induce non-differentiabilities in policy functions. We develop an interpolation technique that addresses this problem directly: It locates the non-differentiabilities and adds interpolation nodes there. To handle this flexible grid, it uses Delaunay interpolation, a simplicial interpolation technique. Hence, we call this method Adaptive Simplicial Interpolation (ASI). We embed ASI into a time iteration algorithm to compute recursive equilibria in an infinite horizon endowment economy where heterogeneous agents trade in a bond and a stock subject to various trading constraints. We show that this method computes equilibria accurately and outperforms other grid schemes by far.     

The impact of credit and fiscal policy under a liquidity trap

This study examines the interaction of non-conventional credit policy and fiscal policy when adverse financial conditions drive the economy to a deep contraction and conventional monetary policy becomes ineffective as the policy interest rate reaches its effective lower bound. Consistent with other studies, under counter-cyclical financial intermediation costs, credit easing policies aimed at reducing credit spread ameliorate the response of the economy and lead to a faster recovery. More importantly, I find that expansionary fiscal policy during an episode of liquidity trap is associated with a large multiplier effect that prevents an otherwise deeper and longer recession. Moreover, the large impact of expansionary fiscal policy is maintained even if credit policy is already in place.     

Measuring the effects of fiscal policy

Measuring the effects of discretionary fiscal policy is both difficult and controversial, as some explicit or implicit identifying assumptions need to be made to isolate exogenous and unanticipated changes in taxes and government spending. Studies based on structural vector autoregressions typically achieve identification by restricting the contemporaneous interaction of fiscal and non-fiscal variables in a rather arbitrary way. In this paper, we relax those restrictions and identify fiscal policy shocks by exploiting the conditional heteroscedasticity of the structural disturbances. We use this methodology to evaluate the macroeconomic effects of fiscal policy shocks in the U.S. before and after 1979. Our results show substantive differences in the economy׳s response to government spending and tax shocks across the two periods. Importantly, we find that increases in public spending are, in general, more effective than tax cuts in stimulating economic activity. A key contribution of this study is to provide a formal test of the identifying restrictions commonly used in the literature.     

The zero lower bound,the dual mandate,and unconventional dynamics

This paper examines monetary policy when it is constrained by the zero lower bound (ZLB) on the nominal interest rate. Our analysis uses a nonlinear New Keynesian model with technology and discount factor shocks. Specifically, we investigate why technology shocks may have unconventional effects at the ZLB, what factors affect the likelihood of hitting the ZLB, and the implications of alternative monetary policy rules. We initially focus on a New Keynesian model without capital (Model 1) and then study that model with capital (Model 2). The advantage of including capital is that it introduces another mechanism for intertemporal substitution that strengthens the expectational effects of the ZLB. Four main findings emerge: (1) In Model 1, the choice of output target in the Taylor rule may reverse the effects of technology shocks when the ZLB binds; (2) When the central bank targets steady-state output in Model 2, a positive technology shock at the ZLB leads to more pronounced unconventional dynamics than in Model 1; (3) The presence of capital changes the qualitative effects of demand shocks and alters the impact of a monetary policy rule that emphasizes output stability; and (4) In Model 1, the constrained linear solution is a decent approximation of the nonlinear solution, but meaningful differences exist between the solutions in Model 2.     

Lack of confidence,the zero lower bound,and the virtue of fiscal rules

In the presence of the zero lower bound, standard business cycle models with a Taylor-type monetary policy rule are prone to equilibrium multiplicity. A drop in private sector confidence can drive the economy into a liquidity trap without any change in fundamentals. I show, in the context of a standard New Keynesian model, that it is possible to design Ricardian fiscal spending rules that insulate the economy from such expectations-driven liquidity traps. In the case of price adjustment costs, desirable fiscal rules ensure that a drop in confidence does not lead to a decline in real marginal costs. In the case of nominal wage adjustment costs, desirable fiscal spending rules ensure that a drop in confidence does not lead to a decline in the ratio of the marginal rate of substitution between private consumption and hours worked relative to the real wage rate.     

Optimal discretionary monetary policy in a micro-founded model with a zero lower bound on nominal interest rate

This paper investigates optimal discretionary monetary policy under the zero lower bound on the nominal interest rate (ZLB) in the case of a distorted steady state due to monopoly and taxation. Solving a fully nonlinear micro-founded (FNL) model using a global method, I find that the central bank in a more distorted economy would cut the interest rate less aggressively under a particularly adverse demand shock. This occurs because inflation and nominal interest rates are higher on average, making the ZLB less likely to bind and causing the economy to escape from the ZLB sooner. However, the social planner would choose the optimal inflation rate of approximately zero. The result emerges because the unconditional benefit of avoiding the ZLB is not big enough to offset the cost of higher relative price dispersion when inflation is significantly positive. In addition, I show that the conventional linear-quadratic (LQ) method is inaccurate in the case of a sufficiently distorted steady state.     

Debt constraints and monetary policy

In the present paper we show how simple monetary policies can mitigate real effects of credit frictions. We consider stationary overlapping generations economies in which consumers are not equally efficient in producing capital and cannot commit to repay loans. The presence of money in itself does not mitigate the real effects of credit frictions. Equilibrium allocations are generally not Pareto optimal unless the returns on money and capital production are identical for more productive consumers. However, printing money and distributing it to young consumers increase their incomes allowing young more productive consumers to produce more capital. Consequently money printing increases output.     

Innovation dynamics and fiscal policy: Implications for growth,asset prices,and welfare

We study the equilibrium implications of different fiscal policies on macroeconomic quantities and welfare by utilizing an endogenous growth model that matches asset pricing data well. The fiscal instruments of interest are (i) subsidies to R&D expenditure, consumption and capital investment, and (ii) cuts in labor and corporate tax rates. Our equilibrium analysis provides new insights on the interplay of innovation dynamics and fiscal policy. Importantly, we find growth and welfare to be inversely related when changing R&D subsidies. However, this depends on how well the model reproduces asset pricing dynamics. Moreover, only subsidies to capital investments and cuts in the corporate tax rate have the potential to increase both growth and welfare.     

A general endogenous grid method for multi-dimensional models with non-convexities and constraints

The endogenous grid method (EGM) significantly speeds up the solution of stochastic dynamic programming problems by simplifying or completely eliminating root-finding. We propose a general and parsimonious EGM extended to handle (1) multiple continuous states and choices, (2) multiple occasionally binding constraints, and (3) non-convexities such as discrete choices. Our method enjoys the speed gains of the original one-dimensional EGM, while avoiding expensive interpolation on multi-dimensional irregular endogenous grids. We explicitly define a broad class of models for which our solution method is applicable, and illustrate its speed and accuracy using a consumption–saving model with both liquid assets and illiquid pension assets and a discrete retirement choice.     

Optimal monetary policy in a new Keynesian model with animal spirits and financial markets

This article presents a macro-finance-interaction model that integrates a NKM with bounded rationality and an agent-based financial market model. We derive four interactive channels between the two sectors where two channels are strictly microfounded. We analyze the impact of the different channels on economic stability and derive optimal (conventional and unconventional) monetary policy rules. We find that coefficients of optimal Taylor rules do not significantly change if financial market stabilization becomes part of the central bank׳s objective function. Additionally, we show that rule-based, backward-looking monetary policy creates huge instabilities if expectations are boundedly rational. Our model is externally validated by showing that it generates fat tailed output growth rates.     

Optimal monetary policy under incomplete markets and aggregate uncertainty: A long-run perspective

This paper examines the role of monetary policy in an environment with aggregate risk and incomplete markets. In a two-period overlapping-generations model with aggregate uncertainty, optimal monetary policy attains the ex-ante Pareto optimal allocation. This policy aims to stabilize the savings rate in the economy by changing real returns of nominal bonds via variation in expected inflation. Optimal expected inflation is procylical and on average higher than without uncertainty. Simple inflation targeting rules closely approximate the optimal monetary policy.     

Economic uncertainty,central bank digital currency,and negative interest rate policy

The COVID-19 outbreak has brought unprecedented social attention to economic uncertainty and negative interest rate policy (NIRP). How does uncertainty affect economic activity, and how effective is a NIRP based on central bank digital currency (CBDC)? To answer the two questions, we constructed a dynamic stochastic general equilibrium (DSGE) model that accommodates sticky prices and wages. The results indicated: (i) Economic uncertainty has substantially reduced investment, output, wage, and loans, which increases unemployment risk. In the short term, it has triggered impulsive consumption by households, while consumption has fallen into a slump in the long run. (ii) After suffering an uncertainty shock, the economy entered short-term stagflation and long-term deflation. The short-term stagflation was mainly caused by resident wage adjustment, and the long-term deflation was due to the decline in effective demand caused by unemployment risk. (iii) CBDC could eliminate the zero lower bound (ZLB) constraint, thereby improving the effectiveness of NIRP. Compared with traditional currency, CBDC-based NIRP could more effectively smooth macroeconomic fluctuations and alleviate the negative impact of an uncertainty shock, which is more conducive to restoring market confidence and promoting economic recovery.     

A Bayesian approach to optimal monetary policy with parameter and model uncertainty

This paper undertakes a Bayesian analysis of optimal monetary policy for the U.K. We estimate a suite of monetary-policy models that include both forward- and backward-looking representations as well as large- and small-scale models. We find an optimal simple Taylor-type rule that accounts for both model and parameter uncertainty. For the most part, backward-looking models are highly fault tolerant with respect to policies optimized for forward-looking representations, while forward-looking models have low fault tolerance with respect to policies optimized for backward-looking representations. In addition, backward-looking models often have lower posterior probabilities than forward-looking models. Bayesian policies therefore have characteristics suitable for inflation and output stabilization in forward-looking models.