Moving beyond the iceberg model: The role of trade relations in endogenizing transportation costs in computable general equilibrium models

Modeling trade and transportation costs is an essential part of multiregional or spatial computable general equilibrium models where interregional trade plays an important rolein shaping economic activity. The majority of such models use the iceberg trade cost approach where part of the produced output (representing the material costs of transportation) is assumed to melt away during transportation. There are a few models which employ a more refined approach with an explicit transportation sector providing transportation services which are then used to ship goods between locations. In this paper we show that this approach, although much more convenient than the iceberg approach, still lacks full usability due to the fact that markets, hence prices are defined at the regional level and as a result, transportation costs can not be endogenous at the trade relation level. Moreover, under regional level market clearing the iceberg and the more detailed approach are equivalent. We propose to refine the definition of market equilibrium and move it to the trade relation level. Using this approach we can gain full advantage of the explicit transport sector in the model with respect to trade cost evolution. We show through simulations that refining the way trade costs are modelled indeed gains new insights, and that moving the market definition to the trade relational level leads to qualitative changes in the effect of labor supply shocks on main model variables. The paper also presents a method to estimate a SAM by reallocating data from standard industries to a transportation sector which is then consistent with the model setup. This SAM can be used to calibrate the refined model with a detailed transportation sector.     

我国航空运输业市场结构演变分析

在阐述市场结构分析的主要理论和方法的基础上,测算了我国主要航空公司近年来市场份额的比重和变化,分析了市场结构变化特点。根据产业经济学中市场结构的相关理论,利用行业集中度和赫芬达尔-赫希曼指数两个指标,结合我国航空运输业的实践,计算了我国航空运输业市场2001—2009年的绝对集中度、HHI指数和倒数N指数,一致得出我国航空运输业是一个寡头垄断型产业,其垄断强弱程度呈"增强—减弱—增强"动态变化。     

Telecommunications/ transportation substitution and energy conservation Part 2

Part 1 of this article reviewed existing research both on attitudes toward telecommunications substitution for travel and on operational experiments with teleconferencing and telecommuting. Part 2 examines major factors influencing substitution, including government policy. It concludes that government policy can significantly facilitate telecommunications substitution for travel and, indeed, the achievement of any real measure of substitution may depend upon proactive government policy. However, this is an unlikely prospect in the current US national policy environment.     

The environmental effect of car-free housing: A case in Vienna

A case-control study of the car-free model housing project in Vienna was conducted to evaluate whether people living in this settlement have more ‘sustainable lifestyles’ than people living in comparable buildings in Vienna. Another aim was to identify the lifestyle characteristics and household activities which significantly influence the environmental impact of the residents of the car-free housing project and a control group. The control group, referred to as the reference settlement, was chosen from a nearby building complex, with similar characteristics, but without the car-free feature. Household consumption patterns were estimated based on interviews in combination with data from the Austrian consumer expenditure survey and the national accounts. The evaluation of household environmental impacts uses emissions estimates from the Austrian national accounting matrices including environmental accounts and data from life-cycle assessments. Households from the car-free settlement have substantially lower environmental impacts in the categories of ground transportation and energy use; their CO₂ emissions of these two categories are less than 50% of those living in the reference settlement. The households in the car-free settlement have somewhat higher emissions in the categories air transport, nutrition, and ‘other’ consumption, reflecting the higher income per-capita. As a result, the CO₂ emissions are only slightly lower than in the reference settlement, but the emissions intensity is 20% lower. Both household groups have significantly lower environmental impacts than the Austrian average reflecting less car use and cleaner heating energy in Vienna.     

Min–Max exact and heuristic policies for a two-echelon supply chain with inventory and transportation procurement decisions

We study the problem in which one supplier delivers a product to a set of retailers over time by using an outsourced fleet of vehicles. Since the probability distribution of the demand is not known, we provide a Min–Max approach to find robust policies. We show that the optimal Min-Expected Value policy can be very poor in the worst case. We provide a Min–Max Dynamic Programming formulation that allows us to exactly solve the problem in small instances. Finally, we implement a Min–Max Matheuristic to solve benchmark instances and show that it is very effective.     

Design of a rail transit line for profit maximization in a linear transportation corridor

This paper addresses the design problem of a rail transit line located in a linear urban transportation corridor. The service variables designed are a combination of rail line length, number and locations of stations, headway and fare. Two profit maximization models, which account for the effects of different transit pricing structures (flat and distance-based fare regimes), are proposed. In the proposed models, the effects of passenger demand elasticity and population density along the urban corridor are explicitly considered. The solution properties of the proposed models are explored and compared analytically, and the indifference condition for the two fare regimes in terms of the operator’s net profit is identified. A heuristic solution algorithm to solve the proposed models is presented. Numerical examples are provided to show the effects of the fare regimes, rail capital cost and urban configuration (in terms of urban population distribution and corridor length) on the design of the rail transit line and the profitability of the rail transit operations.     

塔山煤矿地面输料钻孔设计与应用研究

同煤集团塔山煤矿针对二盘区工作面距离井口较远,材料运输难度大的问题,提出在二盘区对应地面工业广场向井下打钻孔,建立混凝土集运站,通过钻孔向井下运输混凝土物料的方案,钻孔参数:钻孔垂深为500m,0~80m范围开孔φ750mm,安装φ550mm护壁管;80~500m开孔φ500mm,安装φ325×30mm耐磨铸钢管,解决了混凝土运输的问题,具有较大的社会效益和经济效益。     

海运运价指数研究综述

海运运价指数反映航运市场水平的动态变化,对贸易成本有重要影响。结合近些年海运运价指数的文献研究进展,首次对波罗的海干散货运价指数(BDI)、波罗的海原油运价指数(BDTI)以及中国出口集装箱运价指数(CCFI)三个海运运价指数的影响因素、波动周期性和指数预测方法研究领域的成果进行归纳整理和对比分析,为航运公司、船舶中间商的经营决策提供参考。影响因素主要从供需关系下的运输成本、航运市场、经济环境三个因素展开,波动周期结合各航运市场的特征并分析原因,预测方法则围绕线性模型与非线性模型进行比较,在文献述评的基础上指出目前研究的不足与未来的研究方向。     

网销农产品质量控制的影响因素及对策建议

随着越来越多的农户和涉农企业选择了"农产品触网上行",农产品直接销售到户的比例逐渐上升,这给农产品的质量监控提出了更高的要求。在农产品线上销售企业质量控制现状分析的基础上,采用层次回归分析法对产品质量控制的影响因素进行分析,结果显示:提高货源质量、加大物流运输设施设备投入、加大社会监管力度都能起到提高网销农产品质量的作用。研究成果有助于政府、电商平台对网销农产品质量控制提供改进优化方向,为涉农企业的农产品品牌建设提供参考建议。     

交通运输发展与经济增长的均衡分析

杨格概括了交通运输发展与经济增长相互作用的关系,但他认为这种相互作用关系是一种脱离均衡的运动。本文认为,如果将二者的相互作用关系理解为在理论模型中二者互为解释变量,可以将这种关系纳入均衡分析范式中。在给定外生变量条件下,即可求解均衡的交通运输发展规模与均衡的专业化生产规模。均衡规模理论上即是适度经济规模。当交通运输发展规模与专业化生产规模的实际状态处于失衡状态时,经济社会追求利益最大化的机制会使失衡自发地趋向均衡。由失衡趋向均衡的路径有三条：平衡增长战略;交通运输先行战略;交通运输滞后发展战略。如果技术条件或者制度安排发生重大变化,交通运输发展规模与专业化生产规模之间的均衡将会发生变动,即由旧的均衡趋向于新的均衡。规模报酬变动可以为交通运输发展与经济增长的均衡变动提供理论解释。