“Itô's Lemma” and the Bellman Equation for Poisson Processes: An Applied View

Using the Hamilton-Jacobi-Bellman equation, we derive both a Keynes-Ramsey rule and a closed form solution for an optimal consumption-investment problem with labor income. The utility function is unbounded and uncertainty stems from a Poisson process. Our results can be derived because of the proofs presented in the accompanying paper by Sennewald (2006). Additional examples are given which highlight the correct use of the Hamilton-Jacobi-Bellman equation and the change-of-variables formula (sometimes referred to as ``Itô's Lemma'') under Poisson uncertainty.     

World Oil Depletion Models: Price effects compared with strategic or technological interventions

World oil depletion, including natural gas liquids, was modelled in the past by many authors. Recently, Guseo and Dalla Valle have introduced and Guidolin has applied a new approach following perturbed life-cycle diffusion models. Here we examine joint effects of economic and strategic or technological interventions using a Generalized Bass Model (GBM). Statistical analysis takes into account three different hierarchical levels: natural diffusion, long memory interventions and stochastic components. The main results confirm the statistical significance of historical 1970s shocks and highlight a strong long memory effect due to an increase in oil production after World War II. The estimated peak-date, 2007, and the 90% depletion time, 2019, are determined under an equilibrium intervention hypothesis.     

Environmental Policy in Open Economies and Monopolistic Competition

This paper analyses the implications of international trade for non-cooperative environmental policy in the case of local production externalities. A particular focus is on the potential effects of regulations on the variety of goods and the resulting international spillover caused by trade. A tougher domestic standard negatively affects the utility of the households abroad, since such a policy reduces their variety of imports (due to fewer domestic product inventions) or their consumption of each imported brand (due to higher import prices). Ignoring the negative spillover, non-cooperative governments implement inefficiently strict standards in equilibrium. In contrast to this clear-cut inefficiency result, the impact of international trade on the state of the environment is ambiguous.     

Timing of Public Information and Cost Reduction

Received July 31, 2000; revised version received July 18, 2001     

动态比较优势与中国目标产业选择实证分析

通过动态比较优势的理论模型，可揭示后进国家政策介入的必要性和有效性；采用独立随机增量过程马尔可夫链方法，可对中国制造业动态比较优势进行经验验证和预测。结果显示，弱比较劣势产业是目标产业。该些产业的优势状态保持不变或上移的概率高达80％以上，表明它们具有较大的潜在比较优势。     

THE JOINT ARRIVAL AND DEPARTURE PROCESS FOR THE M/M/l QUEUE

We consider the M/M/1-queue and derive an explicit expression for the joint distribution of the number of arrivals and the number of departures in [0, t), given the number of customers initially present. The derivation is almost purely combinatorial, it avoids the use of generating functions, and immediately yields a simple probabilistic interpretation of the result.     

Modelling of repairable systems with various degrees of repair

The availability of a stochastic repairable system depends on the failure behaviour and on repair strategies. In this paper, we deal with a general repair model for a system using auxiliary counting processes and corresponding intensities which include various degrees of repair (between minimal repair and perfect repair). For determining the model parameters we need estimators depending on failure times and repair times: maximum likelihood (ML) estimator and Bayes estimators are considered. Special results are obtained by the use of Weibull-type intensities and random observation times.     

基于交易成本经济学的企业业务外包分析

企业业务外包是近年来在国外兴起的一种经营行为,它的目的是降低成本,提高企业的竞争力。目前中国很多企业也纷纷在尝试这一做法。然而不是任何企业,任何业务都适合外包。本文将从交易成本经济学的角度来对企业业务外包这一行为进行分析,提出适宜进行业务外包的情况,并说明进行业务外包时应该注意的问题。     

Thermodynamics and process analysis for future economic scenarios

Economists are increasingly interested in forecasting future costs and benefits of policies for dealing with materials/energy fluxes, polluting emissions and environmental impacts on various scales, from sectoral to global. Computable general equilibrium (CGE) models are currently popular because they project demand and industrial structure into the future, along an equilibrium path. But they are applicable only to the extent that structural changes occur in or near equilibrium, independent of radical technological (or social) change. The alternative tool for analyzing economic implications of scenario assumptions is to use Leontief-type Input-Output (I-O) models. I-O models are unable to endogenize structural shifts (changing I-O coefficients). However, this can be a virtue when considering radical rather than incremental shifts. Postulated I-O tables can be used independently to check the internal consistency of scenarios. Or I-O models can be used to generate scenarios by linking them to econometric macro-drivers (which can, in principle, be CGE models). Explicit process analysis can be integrated, in principle, with I-O models. This hybrid scheme provides a natural means of satisfying physical constraints, especially the first and second laws of thermodynamics. This is important, to avoid constructing scenarios based on physically impossible processes. Process analysis is really the only available tool for constructing physically plausible alternative future I-O tables, and generating materials/energy and waste emissions coefficients. Explicit process analysis also helps avoid several problems characteristic of pure CGE or I-O models, viz. (1) aggregation errors (2) inability to handle arbitrary combinations of co-product and co-input relationships and (3) inability to reflect certain non-linearities such as internal feedback loops.     

论风险投资中的尽职调查

通过对20多位风险投资家的调研,对他们尽职调查所必备的条件、策略及过程进行了系统分析,总结出其内在规律,以期对我国风险投资项目的筛选有所启示.