Optimal Mortgage Refinancing with Regime Switches

A model of rational mortgage refinancing is developed where the drift and volatility of interest rate process switch between two regimes. Because of the possibility of a regime shift, the optimal refinancing policy is characterized by the different threshold of interest differential for each regime. Numerical simulation demonstrates that the optimal refinancing threshold in each regime can be smaller or larger than the threshold under single-regime models. Finally, we evaluate the predictions of the model, based on the estimated parameters for a two-regime model to capture the evolution of the mortgage rates in the US. Our model can produce both late and early refinancing, which is consistent with the observed refinancing behavior. The views expressed in this paper are solely those of the authors and do not necessarily reflect official positions of the Sumitomo Trust and Banking Co., Ltd.     

Economic policy with bounded controls

When investigating optimal policies for macroeconomic models, it is common practice to modify the objective function so that the resulting optimal control trajectories become acceptable from a practical point of view. In this paper we argue that the sole purpose of the objective function should be to express the preference of the decision makers, and that explicit bounds on the controls should be used to ensure that the optimal controls will be practical. Using a piece-wise quadratic objective function involving only the unemployment and inflation rates, which are state (endogenous) variables, we first develop a discrete minimum principle, giving necessary and sufficient optimality conditions. Then we perform various bounded control experiments with the 35-equation quarterly CLEAR model of the Canadian economy, which is very briefly described. The empirical results which were obtained using a version of the GRG algorithm are discussed in view of the conclusions that might be drawn for a real-world practical policy analysis.     

Segmented asset markets and optimal exchange rate regimes

This paper revisits the issue of the optimal exchange rate regime in a flexible price environment. The key innovation is that we analyze this question in the context of environments where only a fraction of agents participate in asset market transactions (i.e., asset markets are segmented). Under this friction alternative exchange rate regimes have different implications for real allocations in the economy. In the context of this environment we show that flexible exchange rates are optimal under monetary shocks and fixed exchange rates are optimal under real shocks.     

人民币汇率变动的物价传递效应:多结构变化协整回归分析

现有研究物价传递效应的文献以线性模型为主,甚少关注物价传递过程中可能存在的结构变化,本文在充分考虑我国转轨时期所面临的各种经济冲击的条件下,利用最新发展的多结构变化协整回归方法考察了1994年1月至2008年12月间人民币汇率变动的物价传递效应。研究结果表明,人民币汇率变动的物价传递效应分别在1998年8月、2002年10月、2005年8月及2007年7月发生了四次结构变化,传递效应虽总体趋减,但2007年7月后出现了反复,且符号也发生了改变。在上述结论基础上,本文提出了相关政策建议。     

Optimal emission-extraction policy in a world of scarcity and irreversibility

This paper extends the classical exhaustible-resource/stock-pollution model with irreversibility of pollution decay, meaning that after reaching some threshold there is no decay of the pollution stock. Within this framework, we answer the question how the potential irreversibility of pollution affects the extraction path. We investigate the conditions under which the economy will optimally adopt a reversible policy, and when it is optimal to enter the irreversible region. In the case of irreversibility it may be optimal to leave a positive amount of resource in the ground forever. As far as the optimal extraction/emission policy is concerned, several types of solutions may arise, including solutions where the economy stays at the threshold for a while. Given that different programs may satisfy the first order conditions for optimality, we further investigate when each of these is optimal. We show that it is never optimal for the economy to stay at the threshold for a while before entering the irreversible region. The optimality analysis is then illustrated by means of a calibrated example. To sum up, for any pollution level, we can identify a critical resource stock such that there exist multiple optima i.e. a reversible and an irreversible policy that yield exactly the same present value. For any resource stock below this critical value, the optimal policy is reversible whereas with large enough resources, irreversible policies outperform reversible programs.     

中国城市物联网产业发展水平测度及比较

依据中国《物联网"十二五"发展规划》制定的物联网产业统计口径,结合物联网产业链结构的特征,设计包括5个一级指标和20个二级指标的物联网产业发展水平评价指标体系,运用层次分析法(AHP)确定指标权重,以14家物联网上市公司数据为基础,考量中国18个主要城市2009~2011年物联网产业水平。结果显示:整体上,中国物联网产业水平呈上升趋势;东、中、西部地区物联网产业发展水平存在差异;不同城市物联网产业发展的优势不同。     

论言语幽默的不可致笑性——矛盾力量

本文从心理学、认知语言学相结合的视角出发,分析言语幽默的不可致笑性,指出不可致笑也是言语幽默不可忽视的导向之一。通过对矛盾消解理论和心理学参量主观道德标准（SMP）的认同级别（Commitment Level）进行综述,试图对矛盾消解理论进行必要的补充,提出了矛盾力量的概念,试图解释笑话不好笑的原因和结果,使得矛盾消解理论更加科学和完善。     

Optimal tariffs,optimal taxes and economic development

Cross-section and time-series data suggest that nations substitute income taxes for tariffs as they develop. This paper confronts the data within the context of a two-country open-economy endogenous growth model in which public expenditure is financed by an optimal tariff and income tax. When the latter is subject to administrative costs, the model predicts that the government will optimally substitute the income tax for the tariff as output rises along the transition. The model is calibrated and a simulation yields time paths for the shares of total government revenue derived from the tariff and the income tax that are consistent with the data.     

教育管理技术方法研究——课程重要程度的评价

课程重要程度是一个至今没有被定义的概念。如何评价课程重要程度 ,是科学规划课程必须解决的难题。各国课程理论却没有深入研究这一问题。近年来 ,部分学者探索用价值工程、系统工程等管理技术分析课程问题 ,并提出了一些评价方法 ,如打分法、排序法等。但由于至今对课程重要程度的概念理解不一 ,评价结果偏差很大 ,实际效果不理想。本文首先对课程重要程度进行定义 ,并在深入分析的基础上 ,提出了主要评价指标及其关系模型。同时为了模型应用方便 ,提出应用模型应注意的主要问题和相关建议 ,以及用模糊数学评判结果的思路和方法。     

Non-convex optimal portfolio sets and constant relative risk aversion

This paper shows by example that, under constant relative risk aversion (CRRA), the set of optimal portfolios can be non-convex even in the presence of a complete set of Arrow-Debreu securities. This implies that, with exclusively CRRA investors, market models without a strong distributional assumption such as that of the capital asset pricing model cannot be tested by testing the optimality of the market portfolio, or by assuming a representative investor. This demonstration extends the key result of Dybvig and Ross [Dybvig, P. H., & Ross S. A. (1982). Portfolio efficient sets. Econometrica, 50, 1525–1546], who showed an example of non-convexity with less restrictive utility assumptions but which could not apply to the case of a complete set of Arrow-Debreu securities.