Debt stabilization in a Non-Ricardian economy

In models with a representative infinitely lived household, tax smoothing implies that the steady state of government debt should follow a random walk. This is unlikely to be the case in overlapping generations (OLG) economies, where the equilibrium interest rate may differ from the policy maker's rate of time preference. It may therefore be optimal to reduce debt today to reduce distortionary taxation in the future. In addition, the level of the capital stock in these economies is likely to be suboptimally low, and reducing government debt will crowd in additional capital. Using a version of the Blanchard-Yaari model of perpetual youth, with both public and private capital, we show that it is optimal in steady state for the government to hold assets. However, we also show how and why this level of government assets can fall short of both the level of debt that achieves the optimal capital stock and the level that eliminates income taxes. Finally, we compute the optimal adjustment path to this steady state

Optimal public investment, growth, and consumption : evidence from African countries.

How much does public capital matter for economic growth? How large should it be? This paper attempts to answer these questions, taking the case of SSA countries. It develops and estimates a model that posits a nonlinear relationship between public investment and growth, to determine the growth-maximizing public investment GDP share. It empirically also accounts for the crowding-in and crowding-out effects between public and private investment, with equations estimated separately and simultaneously, using System GMM. The paper further runs simulation and examines the public investment GDP share that maximizes consumption. This is estimated to be between 8.4 percent and 11.0 percent. The results from estimating the growth model are in the middle of this range, which is larger than the observed value of 7.2 percent at the end of the sample period. These outcomes suggest that, on average, there has been public under-investment in Africa, contrary to previous finding

Theory of Stochastic Optimal Economic Growth

This paper is a survey of the theory of stochastic optimal economic growth.International Development,

A new comparative approach to macroeconomic modeling and policy analysis

In the aftermath of the global financial crisis, the state of macroeconomic modeling and the use of macroeconomic models in policy analysis has come under heavy criticism. Macroeconomists in academia and policy institutions have been blamed for relying too much on a particular class of macroeconomic models. This paper proposes a comparative approach to macroeconomic policy analysis that is open to competing modeling paradigms. Macroeconomic model comparison projects have helped produce some very influential insights such as the Taylor rule. However, they have been infrequent and costly, because they require the input of many teams of researchers and multiple meetings to obtain a limited set of comparative findings. This paper provides a new approach that enables individual researchers to conduct model comparisons easily, frequently, at low cost and on a large scale. Using this approach a model archive is built that includes many well-known empirically estimated models that may be used for quantitative analysis of monetary and fiscal stabilization policies. A computational platform is created that allows straightforward comparisons of models’ implications. Its application is illustrated by comparing different monetary and fiscal policies across selected models. Researchers can easily include new models in the data base and compare the effects of novel extensions to established benchmarks thereby fostering a comparative instead of insular approach to model development

Sequential δ\delta-optimal consumption and investment for stochastic volatility markets with unknown parameters

We consider an optimal investment and consumption problem for a Black-Scholes financial market with stochastic volatility and unknown stock appreciation rate. The volatility parameter is driven by an external economic factor modeled as a diffusion process of Ornstein-Uhlenbeck type with unknown drift. We use the dynamical programming approach and find an optimal financial strategy which depends on the drift parameter. To estimate the drift coefficient we observe the economic factor $Y$ in an interval $[0,T_0]$ for fixed $T_0>0$, and use sequential estimation. We show, that the consumption and investment strategy calculated through this sequential procedure is $\delta$-optimal.Comment: pages:38. arXiv admin note: text overlap with arXiv:1102.118

Numerical solution of optimal control problems with constant control delays

We investigate a class of optimal control problems that exhibit constant exogenously given delays in the control in the equation of motion of the differential states. Therefore, we formulate an exemplary optimal control problem with one stock and one control variable and review some analytic properties of an optimal solution. However, analytical considerations are quite limited in case of delayed optimal control problems. In order to overcome these limits, we reformulate the problem and apply direct numerical methods to calculate approximate solutions that give a better understanding of this class of optimization problems. In particular, we present two possibilities to reformulate the delayed optimal control problem into an instantaneous optimal control problem and show how these can be solved numerically with a state-of-the-art direct method by applying Bock’s direct multiple shooting algorithm. We further demonstrate the strength of our approach by two economic examples.delayed differential equations, delayed optimal control, numerical optimization, time-to-build