Benteng Zou

BRIDGING THE GAP BETWEEN GROWTH THEORY AND THE NEW ECONOMIC GEOGRAPHY: THE SPATIAL RAMSEY MODEL

We study a Ramsey problem in infinite and continuous time and space. The problem is discounted both temporally and spatially. Capital flows to locations with higher marginal return. We show that the problem amounts to optimal control of parabolic partial differential equations (PDEs). We rely on the existing related mathematical literature to derive the Pontryagin conditions. Using explicit representations of the solutions to the PDEs, we first show that the resulting dynamic system gives rise to an ill-posed problem in the sense of Hadamard. We then turn to the spatial Ramsey problem with linear utility. The obtained properties are significantly different from those of the nonspatial linear Ramsey model due to the spatial dynamics induced by capital mobility.

Habit in pollution. A challenge for intergenerational equity

In this article we extend the recent literature on overlapping generations and pollution by allowing each generations utility to depend on past levels of pollution. To conform with the literature on habit in consumption we call this extension habit in pollution. Habit in pollution can visualize itself as either a concern for the flow of pollution only, or for the stock, or anything in between. We show that habit in pollution has not only significant consequences for the level of pollution and capital, but also for the evolution of utility over time. We observe that habit in pollution can lead to violations of two standard criteria of sustainability, which suggests that habit in pollution can be another source of intergenerational inequity.

On the dynamics of capital accumulation across space

We solve an optimal growth model in continuous space, continuous and bounded time. The optimizer chooses the optimal trajectories of capital and consumption across space and time by maximizing an objective function with both space and time discounting. We extract the corresponding Pontryagin conditions and prove their sufficiency. We end up with a system of two parabolic differential equations with the corresponding boundary conditions. Then, we study the roles of initial capital and technology distributions over space in various scenarios.

Polluting technologies and sustainable economic development

We study how the import of older and more polluting technologies alters the relationship between output and environmental quality in developing countries within a vintage capital framework. Our results show that old technologies prolong the period until which pollution may eventually decrease and cause this turning point to be reached at a higher level of pollution. An empirical analysis using export data of vintage technologies from the US and Europe to developing countries supports our theoretical findings.

Carbon capture and storage and transboundary pollution: A differential game approach

We study the strategic behavior of two countries facing transboundary CO2 pollution under a differential game setting. In our model, the reduction of CO2 concentration occurs through the carbon capture and storage process, rather than through the adoption of cleaner technologies. Furthermore, we first provide the explicit short-run dynamics for this dynamic game with symmetric open-loop and a special Markovian Nash strategy. Then, we compare these strategies at the games’ steady states and along some balanced growth paths. Our results show that if the initial level of CO2 is relatively high, state dependent emissions reductions can lead to higher overall environmental quality, hence, feedback strategy leads to less social waste.

Bridging the Gap between Growth Theory and the New Economic Geography: the Spatial Ramsey Model

We study a Ramsey problem in infinite and continuous time and space. The problem is discounted both temporally and spatially. Capital flows to locations with higher marginal return. We show that the problem amounts to optimal control of parabolic partial differential equations (PDEs). We rely on the existing related mathematical literature to derive the Pontryagin conditions. Using explicit representations of the solutions to the PDEs, we first show that the resulting dynamic system gives rise to an ill-posed problem in the sense of Hadamard (1923). We then turn to the spatial Ramsey problem with linear utility. The obtained properties are significantly different from those of the non-spatial linear Ramsey model due to the spatial dynamics induced by capital mobility.

Does Urbanization Foster Human Capital Accumulation

The literature on growth theory has pointed to the importance of human capital in order to explain the process of economic development. In the present study, we highlight the role played by cities in fostering human capital accumulation. More particularly, building on a simple urban economics model, we perform cross-country estimations, measuring the relation between human capital accumulation and urbanization. Our results support the result according to which more urbanization induces higher rates of human capital accumulation, but only above a certain threshold level of development. This latter result raises policy concerns on issues related to over-urbanization.

Threshold Preferences and the Environment

In this article we study the implication of thresholds in preferences. To model this we extend the basic model of John and Pecchenino (1994) by allowing the current level of environmental quality to have a discrete impact on how an agent trades off future consumption and environmental quality. In other words, we endogenize the semi-elasticity of utility based on a step function. We motivate the existence of the threshold based on research from political science, from arguments based on regulation and standards, cultural economics as well as ecological economics. Our results are that the location of the threshold determines both the potential steady states as well as the dynamics. For low (high) thresholds, environmental quality converges to a low (high) steady state. For intermediate levels it converges to a stable p-cycle, with environmental quality being asymptotically bounded below and above by the low and high steady state. We discuss implications for intergenerational equity and policy making. As policy implications we study shifts in the threshold. Our results are that, in case it is costless to shift the threshold, it is always worthwhile to do so. If it is costly to change the threshold, then it is worthwhile to change the threshold if the threshold originally was su ciently low. Lump-sum taxes may lead to a development trap and should be avoided if there are uncertainties about the threshold or the eff ectiveness of the policy.

On the desirability of tax coordination when countries compete in taxes and infrastructure

In our paper, we demonstrate that when countries compete in taxes and infrastructure, coordination through a uniform tax rate or a minimum rate does not necessarily create the welfare effects observed under pure tax competition. The divergence is even worse when the competing jurisdictions differ in institutional quality. If tax revenues are used to gauge the desirability of coordination, our model demonstrates that imposing a uniform tax rate is Pareto-inferior to the non-cooperative equilibrium when countries compete in taxes and infrastructure. This result is completely reversed under pure tax competition if the countries are sufficiently similar in size. If a minimum tax rate is set within the range of those resulting from the non-cooperative equilibrium, the low tax country will never be better off. Finally, the paper demonstrates that the potential social welfare gains from tax harmonization crucially depend on the degree of heterogeneity among the competing countries.

Initial-irregular oblique derivative problems for nonlinear parabolic complex equations of second order with measurable coefficients

This paper deals with initial-irregular oblique derivative boundary value problems for nonlinear and nondivergence parabolic complex equations of second order in a multiply connected domain, where coefficients of equations are measurable. We first verify the uniqueness of solutions for the above problems, and then give a priori estimates of solutions for the problems. Finally, by using the above estimates and the Leray-Schauder theorem, the existence of solutions of the initial-boundary value problems is proved. The results in this paper are generalizations of corresponding theorems in [1],[4] and [5].