A Non-Unitary Discount Rate Model

The standard economic model of intertemporal decision making assumes that a single discount rate applies equally to discount (dis)utility from all different sources. However, studies such as psychology and behavioral economics have provided evidence that people might discount (dis)utility from different sources at different rates. This paper develops a simple model where the agent discounts utility from consumption at a different rate from disutility of labor supply. We show that in our non-unitary discount rate model, the preferences of the agent are time-inconsistent. The source of the time inconsistency is the difference between relative impatience with consumption and labor supply. It is shown that the policy effects in our model are quite different from those in the standard model. For example, when the agent discounts utility from consumption at a higher rate than the disutility of labor supply, the Friedman rule (the zero nominal interest rate) is no longer optimal. We also make comparisons between our results and those obtained in a model with a time variable discount rate where the preferences are time-inconsistent. It is also shown that the policy effects in our model are quite different from those in a model with a time variable discount rate.Non unitary discount rate, Tax policies, Time-inconsistency, Friedman rule.

Technological Progress and Population Growth: Do we have too few children?

Do we have too few children? We intend to address this question. In developed countries, the fertility rate has declined since WWII. This may cause a slowdown in the growth of GDP in developed countries. However, important factors for the well-being of individuals are per capita variables, like per capita growth and per capita consumption. In turn, the rate of technological progress determines the growth rates of per capita variables. If the population size is increasing, the labour inputs for R&D activity increase, and thus speed up technological progress. As individuals do not take account of this positive effect when deciding the number of their own children, the number of children may become smaller than the socially optimal number of children. However, an increase in the number of children reduces the assets any one child owns: that is, there is a capital dilution effect. This works in the opposite direction. We examine this issue using an endogenous growth model where the head of a dynastic family decides the number of children.Technological Progress, Fertility, R&D

UAV/UGV Autonomous Cooperation: UAV Assists UGV to Climb a Cliff by Attaching a Tether

This paper proposes a novel cooperative system for an Unmanned Aerial Vehicle (UAV) and an Unmanned Ground Vehicle (UGV) which utilizes the UAV not only as a flying sensor but also as a tether attachment device. Two robots are connected with a tether, allowing the UAV to anchor the tether to a structure located at the top of a steep terrain, impossible to reach for UGVs. Thus, enhancing the poor traversability of the UGV by not only providing a wider range of scanning and mapping from the air, but also by allowing the UGV to climb steep terrains with the winding of the tether. In addition, we present an autonomous framework for the collaborative navigation and tether attachment in an unknown environment. The UAV employs visual inertial navigation with 3D voxel mapping and obstacle avoidance planning. The UGV makes use of the voxel map and generates an elevation map to execute path planning based on a traversability analysis. Furthermore, we compared the pros and cons of possible methods for the tether anchoring from multiple points of view. To increase the probability of successful anchoring, we evaluated the anchoring strategy with an experiment. Finally, the feasibility and capability of our proposed system were demonstrated by an autonomous mission experiment in the field with an obstacle and a cliff.Comment: 7 pages, 8 figures, accepted to 2019 International Conference on Robotics & Automation. Video: https://youtu.be/UzTT8Ckjz1

Fundamental Study on Instability of Tunnel in Consideration of Post-Peak Strain Softening Behavior of Rock

The main concerns of the present study are, firstly, to formulate the finite element analysis based on the principle of the “stress transfer method”, by which the influnce of the post-peak strain softening behavior of rock, which is one of the intrinsic natures of rock like material, can be appropriately investigated with regard to instability of an underground cavity excavated in rock. Since very little information is available in rock mechanics literature on the post-peak strain softening behav ior, and since no versatile constitutive law is as yet established to be readily employed in a numerical analysis, the analysis is presently conducted by assuming the idealized stress-strain relation and the modified Mohr-Coulomb failure criterion for practical usage. Secondly, the instability of a tunnel possibly caused by the excavation is studied. The analysis reveals a new finding with regard to the mechanism of the instability of a tunnel, such as the falling-off of the tunnel roof and rock burst, which has not been completely manifested so far. As would be anticipated, the shear failure might possibly be developed in a region where the stress concentration arises in relation to the initial stress system in the rock mass and the failure strength of rock. When the strain softening behavior is taken into consideration, the “most critical failure”, (by which the rock loses completely the resitance due to the simultaneous emergence of the mode of shear failure as well as tensile failure), may be subsequently caused as a result of the stress release and the transfer from the previously failed element, the failure zone of which is formed as a cone in shape. This analytical solution is reasonably consistent with the field observation of the instability of a tunnel which takes place under a special stress condition, for instance, a region where a very high horizontal stress remains in the rock formations, as in Ontario, Canada. This is also true in a case where a tunnel is excavated in mountains where a very high overburden pressure might be acting.

Dynamic analysis of reductions in public debt in an endogenous growth model with public capital

* Revised： [12-08-Rev.2, 2014]* Revised： [12-08, 2012]* Revised： [12-08-Rev., 2013

Welfare and Tax Policies in a Neoclassical Growth Model with Non-unitary Discounting

When an individual uses di¤erent discount rates for di¤erent sources of utilities, we call it non unitary discounting. We show that a decision making of the individual becomes time inconsistent. We examine a sim-ple neoclassical growth model with endogenous labor supply in which an individual discounts the utility of consumption and utility of leisure dif-ferently. We derive competitive equilibria in which individuals behave in a time consistent way. We investigate welfare performances of the econ-omy by comparing the allocation of competitive equilibria and that by a central planner. The planner cannot commit its initial decisions like the individual. Thus, the planner must solve the allocation problem in a time consistent way. The welfare performance of the allocation by the cen-tral planner dominates that of the competitive equilibria from an initial point of view; however, the opposite result obtains from a future point of view. We \u85nally examine whether a government can reconcile this welfare conict by using tax policies

Debt Policy Rules in an Open Economy

* Revised：Fiscal Sustainability, Macroeconomic Stability, and Welfare under Fiscal Discipline in a Small Open Economy [13-07, 2013