林业投资均衡性的理论分析

我国林业投资体制的改革面临着许多新的课题,研究市场经济条件下林业投资状况十分必要。首先,从均衡理论出发,在分析宏观经济政策对林业的影响和林业投资现状基础上,对形成这种状况的主要原因进行了探讨;其次,以林业投资对象为主体,对其微观经济行为的成本与收益问题进行了分析;最后,提出深化林业投资体制改革要促进投资主体多元化,给予林业更多的政策扶持,进一步完善林业法律法规,以促进我国林业持续稳定地发展。     

Improving the contributions of technology assessment to the health care system of the U.S.A.

Summary Based on 14 case studies of highly effective therapies and the reasons they succeeded less frequently than they could, we propose a variety of steps to improve the health care system of the U.S.A. Whatever proposal emerges from current national debates until innovations are shown to be safe and effective, they should not be supported; when slightly better technologies are much more expensive than other good ones we need to consider appropriate choices carefully; simplified billing and bookkeping would reduce our costs; when a technology is rapidly introduced cautionnary measures may be needed; tracking immunization and repairing their omissions requires a new system; educational programs such as seen effective in hypertension should be applied in other areas such as vaccination; in organ transplantation the nation should consider “presumed consent”; our payment system sometimes creates perverse incentives and therefore needs review; and the preferences of the public in allocation of health resources need to be discovered once the public is informed about the issues. Research supported by Andrew W. Mellon Foundation.     

The transition to parenthood in Puerto Rico: Occupational status and the timing of first births

This study examines the relationship between occupational status and fertility timing during a period of rapid development in Puerto Rico. Our fundamental hypothesis is that women with higher status occupations face greater opportunity costs than those with less valued jobs and therefore will be more likely to postpone parenthood until later ages than women without such high costs. We test this hypothesis using event history techniques with data from the 1982 Puerto Rico Fertility and Family Planning Assessment, an island-wide survey of women between the ages of 15 and 49. The analysis examines the effects of occupational status on the timing of first births, and finds strong support for the basic hypothesis, especially regarding the post-ponement of teen births. After the teen years, the effects are less pronounced. Overall, it appears that employment opportunities have played an important role in childbearing decisions in Puerto Rico.An earlier version of this paper was presented at the annual meeting of the Population Association of America, Denver, Colorado, 30 April–2 May 1992.     

基于碳标签制度的两级供应链协调机制研究

以市场需求随机的视角建立Stackelberg博弈模型,研究基于碳标签制度的供应商和零售商组成的两级供应链协调策略。模型引入产品碳足迹e₁作为决策变量,分别研究了在收益共享与成本共担契约下集中决策和分散决策中决策变量最优解及最优利润的变化情况。研究结果表明,在考虑碳排因素时集中决策相比于分散决策具有明显的优势;在参数满足一定条件下零售商通过与供应商共担碳减排成本,可以实现利润的增长,初步验证模型的契约设计的有效性。     

具有卖空总量限制的多阶段M—SAD投资组合优化

文章提出具有卖空总量限制、阈值约束和V型交易成本的多阶段均值—半绝对偏差（M-SAD）投资组合优化模型。该模型分别运用均值和半绝对偏衡量资产的收益率和风险。由于交易成本的存在,该模型不满足无后效性的动态优化问题。文章将该模型近似为一般动态规划问题,提出一种新的离散迭代方法,并证明该算法是线性收敛的。最后,文章通过实证研究比较分析卖空总量限制和风险偏好系数取不同值时对投资组合最优策略的影响,验证模型和算法的有效性。     

社会资本、信息渠道对牧户草场转入行为的影响——基于草场流转市场转型背景的分析

基于草场流转市场转型背景,利用内蒙古自治区和甘肃省820个牧户调查数据,实证检验了社会资本、信息渠道对牧户草场转入行为的影响及二者间的作用关系,并进一步探讨了交易费用的中介效应和代际差异的调节效应。结果表明:(1)转型市场下,社会资本仍能促进牧户草场转入,但作用方式发生变化,表现为关键网络节点和牧户主动利用社会网络能力的作用凸显,社会资本总量和被动依赖社会网络信息资源流入的作用式微。(2)网络信息渠道促进了牧户草场转入,但尚未对社会资本形成替代,社会资本与网络信息渠道并行不悖。(3)社会互动通过降低草场流转的交易费用促进了牧户草场转入,而关键网络节点、网络信息渠道不存在相应机制。(4)社会资本、网络信息渠道对牧户草场转入行为的影响存在显著的代际差异,表现为新生代牧户转入草场更加依赖网络信息渠道,中生代、老生代牧户转入草场仅依赖社会资本。据此,建议在建立和完善网络和实体草场流转交易平台等方面完善草场流转市场。     

Effects of fixed costs in two-person sequential bargaining

Rubinstein (1982) considered the problem of dividing a given surplus between two players sequentially, and then proposed a model in which the two players alternately make and respond to each other's offers through time. He further characterized the perfect equilibrium outcomes, which depend on the players time preferences and order of moves. Using both equal and unequal bargaining cost conditions and an unlimited number of rounds, two experiments were designed to compare the perfect equilibrium model to alternative models based on norms of fairness. We report analyses of final agreements, first offers, and number of bargaining rounds, which provide limited support to the perfect equilibrium model, and then conclude by recommending a shift in focus from model testing to specification of the conditions favoring one model over another.     

Adaptive Build-up and Breakdown of Trust: An Agent Based Computational Approach

This article employs Agent-Based Computational Economics (ACE) to investigate whether, and under what conditions, trust is viable in markets. The emergence and breakdown of trust is modeled in a context of multiple buyers and suppliers. Agents develop trust in a partner as a function of observed loyalty. They select partners on the basis of their trust in the partner and potential profit, with adaptive weights. On the basis of realized profits, they adapt the weight they attach to trust relative to profitability, and their own trustworthiness, modeled as a threshold of defection. Trust and loyalty turn out to be viable under fairly general conditions.     

Tactical production and distribution planning with dependency issues on the production process

Tactical production-distribution planning models have attracted a great deal of attention in the past decades. In these models, production and distribution decisions are considered simultaneously such that the combined plans are more advantageous than the plans resolved in a hierarchical planning process. We consider a two-stage production process, where in the first stage raw materials are transformed into continuous resources that feed the discrete production of end products in the second stage. Moreover, the setup times and costs of resources depend on the sequence in which they are processed in the first stage. The minimum scheduling unit is the product family which consists of products sharing common resources and manufacturing processes. Based on different mathematical modelling approaches to the production in the first stage, we develop a sequence-oriented formulation and a product-oriented formulation, and propose decomposition-based heuristics to solve this problem efficiently. By considering these dependencies arising in practical production processes, our model can be applied to various industrial cases, such as the beverage industry or the steel industry. Computation tests on instances from an industrial application are provided at the end of the paper.     

Optimal cut-off for rare events and unbalanced misclassification costs

This paper develops a method for handling two-class classification problems with highly unbalanced class sizes and misclassification costs. When the class sizes are highly unbalanced and the minority class represents a rare event, conventional classification methods tend to strongly favour the majority class, resulting in very low detection of the minority class. A method is proposed to determine the optimal cut-off for asymmetric misclassification costs and for unbalanced class sizes. Monte Carlo simulations show that this proposal performs better than the method based on the notion of classification accuracy. Finally, the proposed method is applied to empirical data on Italian small and medium enterprises to classify them into default and non-default groups.