Economic mobility along the business cycle. The case of Peru

The performance of Latin American countries in reducing poverty and expanding the middle class has been remarkable. By taking a close look at the Peruvian experience, we examine how this aggregate behavior relates to business cycle conditions and whether different population groups share this behavior. We find that social mobility is cyclical; it decreases in recessions but increases with strong economic growth. The reduction in poverty in Peru appears to be the result of a sustained increase in the poverty exit rate together with a prolonged decrease in the poverty entry rate. These results hold among heterogeneous groups and are particularly marked for households regarded as initially disadvantaged.     

The replicator dynamics does not lead to correlated equilibria

It is shown that, under the replicator dynamics, all strategies played in correlated equilibrium may be eliminated, so that only strategies with zero marginal probability in all correlated equilibria survive. This occurs in particular in a family of 4×4 games built by adding a strategy to a Rock-Paper-Scissors game.     

产业集聚效应的系统动力学模型研究

以系统动力学理论为基础，结合产业集聚效应的正反馈特征，对人才流、技术流、资金流和市场流的因果关系进行了探讨。通过产业集聚效应衡量方法的比较，构建系统动力学模型，分析制约产业集聚效应发挥的主要因素，提出加强政府投资力度、发挥市场机制作用和提高企业整体能力的建议。     

Unemployment dynamics in an OLG economy with public pensions

Pension benefits in old age establish a disincentive to save in youth, thereby yielding lower levels of capital stock and the wage rate. As a result, the trade union has an incentive to change the composition of its two targets: employment and the wage rate. This paper develops a model that includes employment effects of public pensions via capital accumulation and union wage setting. Within this framework, we consider how contribution rates to the pension system influence the level and time path of the unemployment rate. It is demonstrated that (1) a higher contribution rate results in a lower unemployment rate, and (2) the economy with a high (low) contribution rate experiences monotone convergence towards (oscillatory convergence towards or a period-2 cycle around) the steady state. The author would like to thank an anonymous referee, Kazutoshi Miyazawa, and seminar participants at Osaka University for their useful comments and suggestions, and Masako Ikefuji and Hiroaki Yamagami for their research assistance. Financial support from the Japan Society for the Promotion of Science (JSPS) through a Grant-in-Aid for Young Scientists (B) (No.17730131), the Asahi Glass Foundation, the Japan Economic Research Foundation and the 21st Century COE Program (Osaka University) is gratefully acknowledged. All remaining errors are mine.     

Ecological Transfers in Non-Human Communities Parallel Economic Markets in a General Equilibrium Ecosystem Model

Synopsis: The oft-cited analogies between ecological and economic systems are exploited to develop a many-species model of population dynamics. In economies, markets are the fundamental institutions in which the interaction of demands and supplies determine the quantities and prices of goods. However, economic markets are not appropriate for ecological communities, because markets rely on voluntary exchange, whereas plants and animals engage in involuntary transfers of biomass. A properly defined counterpart to markets based on biomass transfers permits a general equilibrium model of predator/prey and competitive interactions in a many-species community. Functional response from optimal foraging and predation risk provide the demand and supply, respectively, in the biomass transfers. Energy per unit time is scarce and predators and prey make optimum choices with respect to functional response and risk avoidance based on required energy expenditures. The energy expenditures are similar to economic prices: they determine foraging strategies and are beyond the control of the predators and prey, yet they are determined by the aggregate choices of all predators and prey and by population densities. The energies acquired from foraging are used in a new way to construct difference equations that determine the population dynamics. This revised version was published online in July 2006 with corrections to the Cover Date.     

The British low-wage sector and the employment prospects of the unemployed

Are low wages a way for the unemployed to switch to higher-paying jobs? Using data from the British Household Panel Survey, the labour market dynamics of unemployed, low-paid and higher-paid employed men are analysed. Moreover, the respective (un)employment duration and occupational skill level are accounted for. Results show that in general low wages significantly reduce the risk of future unemployment and increase the chances of ascending the salary ladder, especially in the case of long-term unemployment (>360 days). Furthermore, the occupational skill level has a substantial influence on the upward mobility of low-paid jobs: individuals working in the initial period in a low-paid and higher-skilled occupation have on average an 11 percentage points higher probability of entering higher pay compared to when working in a low-paid and low-skilled occupation.     

企业现金流转系统动态仿真研究

本文运用系统动力学方法分析了企业现金流转问题的基本特征。针对一特定民营企业建立了企业现金流转的系统动力模型，并在此基础上，设计四种仿真方案模拟了不同条件下企业现金流转的具体情况，以期为企业现金流以及企业的持续经营做一些有益的探索。     

顾客需求的非对称性和动态性对新产品开发的影响

在分析顾客需求的非对称性和动态性的基础上，把产品的属性划分为必备、单向、吸引三类，结合客户需求变化、竞争产品策略和产品生命周期理论，为企业的产品创新提供了全新的视角：     

干旱区土地利用结构调整的SD模型研究：以新疆吐鲁番市为例

土地利用结构的调整是我国目前土地利用总体规划的两大核心内容之一。我国干旱地区生态环境十分脆弱、稳定性差。土地沙漠化、盐碱化、草场退化等现象十分严重，本文以新疆吐鲁番市为例．分析了该市土地利用现状和存在的问题．运用系统动力学模型．建立了土地利用结构调整的动态模型，充当地制订中长期土地利用总体规划提供科学依据。     

Protecting Forests Through Farming. A Dynamic Model of Nontimber Forest Extraction

Forest resource extraction by local communities has been cited as a major impediment to the efficient management of protected forests. This paper develops a two sector dynamic model for farming and forest resource extraction by communities living in the forest periphery. The model assumes that land under forestry is constant and households allocate their time to farming and forestry. Comparative dynamic results suggest that higher prices for agriculture output, lower input prices, better knowledge of farming techniques and a lower discount rate may result in a higher equilibrium stock of forest resources. Tobit analysis with primary data collected from the Sinharaja forest in Sri Lanka provides supportive empirical evidence.