Scale-Economy Conditions for Spatial Variation in Farm Size

Given the usual neoclassical assumptions of economic rationality, perfect competition, long-term spatial equilibrium, a Thunian context, and perfectly divisible labor and capital, this paper expresses economies of scale in farming in terms of the yield derived from a given level of intensity. If yield increases as farm scale increases, there are economies of scale. If yield decreases, there are diseconomies of scale. The literature on scale economies in agriculture suggests that scale economies accrue from increases in capital inputs, but diseconomies occur as a result of increases in farm area. The models of the spatial structure of agriculture, with farm size included, show the following: 1. Unless there are economies of scale giving way to diseconomies of scale with increases in farm size, no optimal farm area or farm scale can be defined; 2. If the optimal intensity for farming does not vary over space, the optimal farm scale or area should be constant over space; 3. If intensity varies spatially, and if the optimal economies of scale are a function of area only, farm areas should not vary spatially, and sales volume per farm should increase as market access and fertility increase; 4. It is only if intensity varies spatially and optimal scale economies are a function of both area and total quantities of nonland inputs per farm that farm area should increase as distance to market increases or fertility decreases. In this last case, quantities of nonland inputs per farm should also decrease, and usually sales volume per farm should decrease also.     

Maximizing Accessibility on Congested Networks

The problem of locating facilities to maximize their accessibility on networks where costs are functions of flow volume is considered. In particular, an accessibility model developed by Leonardi is extended to bipartite and tree networks whose arc costs are determined by a flow-dependent congestion function. The resultant nonseparable equilibrium problem is solved heuristically, and numerical simulations are used to explore the model's behavior under varying conditions.     

EXTERNALITIES AND PARTIAL TAX REFORM: DOES IT MAKE SENSE TO TAX ROAD FREIGHT (BUT NOT PASSENGER) TRANSPORT?*

ABSTRACT Externalities such as pollution and road congestion are jointly produced by the use of intermediate inputs by firms and the consumption of final goods by households. To cope with such externalities, policy proposals often suggest partial tax reforms. This paper uses a simple general equilibrium model to explore the effects of a reform of taxes on freight transport in a second‐best setting. The theoretical model shows that the welfare effect of higher freight taxes is positive, unless passenger transport is severely under‐taxed and the tax reform attracts substantially more passenger transport. Moreover, the optimal freight tax may be below or above marginal external cost. Budgetary neutral tax reform exercises with a numerical simulation model for the U.K. suggest that, under a wide variety of parameter values, higher freight transport taxes are indeed welfare increasing. The welfare gain of freight tax reform rises with the level of the passenger tax, but the optimal freight tax declines at higher taxes on passenger transport. Substantial net benefits of tax reform are obtained only under labor tax recycling of the revenues.     

NETWORK LOADING VERSUS EQUILIBRIUM ESTIMATION OF THE STOCHASTIC ROUTE CHOICE MODEL MAXIMUM LIKELIHOOD AND LEAST SQUARES REVISITED*

Daganzo (1977, 1979), Daganzo and Sheffi (1977), Sheffi (1985), and Sheffi and Daganzo (1980) have used one assumption about traveler behavior in developing estimation techniques for the stochastic route-choice problem and another assumption in predicting flows on networks by using the same model. In estimation, they calculate the congested travel costs of the network links from observed flows on the network, and the network is loaded based on these costs. In prediction, they follow their stochastic user-equilibrium assumption by which travelers evaluate costs using the mean of the observed flows (or equilibrium flows). The travel-cost coefficient obtained from the loading method systematically overestimates the true travel-cost coefficient from which the observed flow data (which must be used in loading) is generated. The estimates of the same coefficient, obtained in this paper, by constraining the estimation results to conform to the equilibrium conditions are unbiased, and only marginally less efficient (have larger standard deviations). The average percentage error and inefficiency of the link flow predictions based on the loading method increases as the level of congestion on the network rises. In contrast, the average percentage error of link flow predictions based on the equilibrium estimation method declines and their efficiency remains very high as the level of congestion on the network rises.     

Pricing, Capacity Choice, and Financing in Transportation Networks

Abstract.  This paper explores interrelations between pricing, capacity choice, and financing in transportation networks. We build on the Mohring‐Harwitz result on self‐financing of optimally designed and priced roads and investigate it in a network environment under various types of second‐best regulation. A small network model with endogenous car ownership demonstrates that optimal congestion pricing and capacity choice over an entire network may cause user prices to increase more in initially mildly congested areas compared to heavily congested areas. Furthermore, a flat kilometer charge under optimal capacity choice may result in first‐best efficiency gains.     

RETAIL AMENITIES AND URBAN SPRAWL

This paper examines the interaction between local retail markets and population density in cities. We demonstrate that welfare costs of urban sprawl need not come only from road congestion or environmental externalities, as often suggested in the literature. A city also forgoes potential agglomeration economies in retail when it settles into a spatially sprawling equilibrium. Our theory predicts an additional spatial equilibrium where the city is inefficiently dense, characterized by strong retail agglomeration economies within the core.     

Probing A Traffic Congestion Controversy: A Comment

Ohta (2001) claims to have resolved a die-hard controversy on traffic congestion modeling by defining an inverse aggregate demand function that has traffic density as its argument—in Ohta's terminology the 'primitive term.'Using this demand function, Ohta shows that 'hypercongestion' may very well be an optimal stationary state. This contribution argues that at least if what road users demand is completed trips, and if time spent on the road while traveling implies a cost, then Ohta's approach is fundamentally flawed. Also the conclusion that hypercongestion can be optimal is no longer valid.     

Ray-tracing the paths of very low latitude whistler-mode signals

VLF whistler-mode signals with very low group delays (75–160 ms) received at night in Dunedin, N.Z., from the 23.4 kHz MSK transmissions of NPM, Hawaii (21.5°N, 158°W), are explained by ray-tracing along unducted paths. The typical vertical and horizontal electron density gradients of the night equatorial ionosphere are found to be sufficient to explain not only the typical group delays but also their decrease during the night and the typical frequency shifts observed on these signals. An important feature appears to be the decreasing starting and finishing latitudes (and the decreasing maximum height of the path) during the course of the night. The amplitude of the signals in relation to the expected collisional absorption in the ionosphere is discussed. A simple but quite accurate analytical expression suitable for ray-tracing is derived for the night electron density in the height range 170–1400 km, based on non-isothermal diffusive equilibrium and O⁺/O friction.     

Duopoly prices under congested access*

Abstract. Consider two firms, at different locations, supplying a homogenous good at constant marginal production cost. Consumers incur travel costs to the firm for each unit purchased, and the travel costs increase with the amount of travel to each firm (congestion). When all traffic and all congestion are generated by travel to a duopolist, both the Nash–Bertrand equilibrium prices and the Nash–Cournot equilibrium prices exceed the sum of the marginal production cost and the marginal external travel cost. However, when the road is shared by travelers to the duopolists' facilities and travelers in competitive markets, the Nash–Bertrand duopoly price equals the competitive price and the Nash–Cournot price contains a markup.     

The general equilibrium effects of high-occupancy vehicle lanes on congestion,sprawl, energy use,and carbon emissions

High-occupancy vehicle (HOV) lanes have been promoted to encourage carpools, reduce traffic congestion, and improve air quality. At the partial equilibrium level, commuting with three workers per automobile clearly reduces highway congestion, lowers carbon emissions, and saves energy compared with three single drivers. This paper develops a numerical urban simulation model to generate the general equilibrium effects of HOV lanes on urban spatial structure, energy use, and greenhouse gas emissions. The major findings are that while HOV lanes reduce traffic congestion and improve welfare, the fall in transportation cost leads to urban sprawl, which results in higher dwelling energy use and a larger carbon footprint. Overall, the HOV lane policy has little effect on total energy consumption and carbon emissions. This is another classic case of general equilibrium effects reversing the partial equilibrium effects of an urban policy. In contrast, a gasoline tax policy leads to less urban sprawl but is less effective at lowering energy consumption and carbon emissions. Imposing congestion tolls is a more effective tool at reducing traffic congestion, saving energy, and lowering carbon emissions.     

Optimizing the Spatial Structure of the Agricultural Production Function

Important characteristics of spatial agricultural production functions are derived by introducing a non‐negative curvilinear spatial demand function for production input intensities. Given the usual neoclassical rationale assumptions of spatial demand for capital and labor inputs under competitive environment of farming in developing agricultural economies, the optimal production levels are determined by optimizing spatial demand for production inputs. Decreasing price‐to‐transport costs ratio (that is, decrease in the prices of capital goods or increase in freight rates) and increasing wage‐to‐travel costs ratio (that is, increase in labor wages or decrease in the travel rate) expand the limits of the (spatial) optimal boundary of the demand for agricultural capital goods and labor input respectively. These effects occur on account of the operation of (positive) spatial price gradient and (negative) wage‐gradient in the market region. It may be noted that elasticities of demand for production factors are spatially variant and have significant effects on the alterations in the structure of agricultural production. However, the spatial optimal solution of production has a complicated relationship with them. The price elasticity has negative and wage elasticity has positive spatial gradients in the market region. Farmers located in the periphery of the market region are not much affected by the proportionate changes occurring in the prices of agricultural capital goods but are more sensitive to the proportional changes in labor wages. Because of a decreasing trend in capital input demand and increase in labor input with distance from the market, capital‐product diminishes with a decreasing rate and labor‐product increases with an increasing rate in the spatial structure of agricultural production. As a result, capital‐labor ratio falls toward zero, which raises profit rate per unit of capital investment especially in the outer part of the market region. The equilibria of optimal production with price elasticity as well as of capital intensity with labor employment (that is, capital‐labor ratio as unity) determine spatial limits of the optimal production zone which is shifted outward subject to the provision of cheap transportation, stabilizing market prices and/or increasing wage rate at the market center. It will help in extending outwardly the optimal spatial limits of capital investment and will mobilize capital resources of farmers in the periphery for efficient and competitive capital‐dominated farming.     

Computing geochemical mass transfer and water/rock ratios in submarine hydrothermal systems: implications for estimating the vigour of convection

A method of calculating chemical water/rock ratios is presented that enables the estimation of fluid velocities in open, flow‐through hydrologic systems. The approach is based on relating the gain/loss of a chemical species per kilogram of solid phase to the loss/gain of that species in the fluid phase, integrated across a specified length of the flowpath. After examining the underlying approximations of the approach using a one‐dimensional model of seawater moving through a basalt under nonisothermal conditions, the method is applied to representative zones within a two‐dimensional hydrothermal convective system. The method requires that regions within the flow system can be identified in which the direction of flow is steady for an extended period of time. Estimates of fluid velocity are spatial and temporal averages for the length of the flowpath used in the calculation. The location within the flow system and the nature of the alteration reactions determine which species can provide reliable values of the chemical water/rock ratio and useful estimates of fluid velocities. Over the length of the flowpath considered, the calculation of water/rock ratios works best when a species is controlled by a single reaction. Accurate estimates are favoured if the concentration profile of a species along the flowpath increases or decreases monotonically. If the length of the flowpath extends over more than one reaction zone, then erroneous estimates of the water/rock ratio and fluid velocity are more likely. Model calculations suggest that the quartz/silica system should provide reliable estimates for fluid velocity under a wide range of temperature and flow conditions, in particular in those regions of a system at or near quartz equilibrium, so that the aqueous silica concentration is buffered by quartz and correlated with the temperature distribution.     

Agglomeration Diseconomies of Traffic Congestion and Agglomeration Economies of Interaction in the Information-Oriented City

This paper presents a partial equilibrium model of land, labor, and transportation markets in an information-oriented city with traffic congestion of commuting and agglomeration economies of interaction. We derive the equilibria by numerical computations using specific utility, production, and congestion functions. The laissez-faire equilibrium is compared with the optimum. In contrast with the results of many previous papers, at the optimum the CBD becomes compact and the city more suburbanized than the laissez-faire equilibrium. We also analyze the effects of a Pigouvian tax system and subsidies on the spatial structure in the city.     

聚集经济与最优城市规模探讨

经济活动的空间集中是一个引人注目的现象,聚集经济是空间集中的重要原因之一。虽然外部性对经济活动的集中有重要影响,但要解释聚集经济的来源还必须寻求更微观、更基本的经济主体行为上的原因。每个城市都存在着一个最优的规模,这个最有效率的规模是由经济活动空间集中所带来的利益与所引起的成本之间的一个均衡所决定的。因此,在城市化过程中,必须注重城市功能与效率的充分发挥。本文结合规模收益递增和单中心圆形城市模型,分析了通勤成本、城市规模收益递增程度对最优城市规模的影响,讨讨了城市人均收入与城市规模之间的关系,推导了两种对立的力量所决定的最优城市规模。文中指出:在一定条件下,城市人均收入与城市规模之间存在倒U形关系;否则,在城市总生产函数中规模收益递增程度足够强的情况下,最优城市规模取决于通勤成本。     

URBAN GROWTH EXTERNALITIES AND NEIGHBORHOOD INCENTIVES: ANOTHER CAUSE OF URBAN SPRAWL?*

ABSTRACT This paper suggests a cause of low density urban development or urban sprawl that has not been given much attention in the literature. There have been a number of arguments put forward for market failures that may account for urban sprawl, including incomplete pricing of infrastructure, environmental externalities, and unpriced congestion. The problem analyzed here is that urban growth creates benefits for an entire urban area, but the costs of growth are borne by individual neighborhoods. An externality problem arises because existing residents perceive the costs associated with the new residents locating in their neighborhoods, but not the full benefits of new entrants which accrue to the city as a whole. The result is that existing residents have an incentive to block new residents to their neighborhoods, resulting in cities that are less dense than is optimal, or too spread out. The paper models several different types of urban growth, and examines the optimal and local choice outcomes under each type. In the first model, population growth is endogenous and the physical limits of the city are fixed. The second model examines the case in which population growth in the region is given, but the city boundary is allowed to vary. We show that in both cases the city will tend to be larger and less dense than is optimal. In each, we examine the sensitivity of the model to the number of neighborhoods and to the size of infrastructure and transportation costs. Finally, we examine optimal subsidies and see how they compare to current policies such as impact fees on new development.     

Congestion Tolling and Urban Spatial Structure

According to the standard model of urban traffic congestion and urbanspatial structure, congestion tolling results in a more concentrated city. In recent years, a new model of rush-hour urban auto congestion has been developed that incorporates trip-timing decisions—the bottleneck model. In the simplest bottleneck model optimal congestion tolling without toll-revenue redistribution has no effect on trip price because the efficiency gainsexactly equal the toll revenue collected. Optimal congestion tolling then has no effect on urban spatial structure. This paper formalizes and extends this result.     

Recent Theoretical Paradigms in Urban Growth

The aim of this article is to present a critical view of the theoretical toolboxes developed in urban economics to explain urban city size. The article starts with the consideration that, during the 1960s and 1970s, the question of optimal city-size tended to be expressed in a misleading way. The real issue is not an “optimal city size” but an “efficient size”, which depends on the functional characteristics of the city and on the spatial organization within the urban system. Economies of scale exist up to a certain city size. However, urban development generates conditions leading to structural readjustments which lead to new economic advantages. These structural adjustments may be either sectoral transformations towards higher-order functions, or the emergence of external linkages with other cities. The article provides recent empirical evidence of the role played by urban functions and city networking in explaining urban equilibrium size. The empirical analyses reported here witness the importance of the structural adjustment of cities needed to achieve a higher equilibrium size.     

长江经济带交通基础设施空间均衡度研究

利用1997-2013年长江经济带各省份数据,研究了交通基础设施空间均衡和极化程度及其影响因素,并构建动态面板数据模型,采用系统GMM估计进行了实证检验。研究结果表明:长江经济带交通基础设施发展较快,但存在空间非均衡和空间极化特征;铁路密度和公路密度的空间非均衡程度依次递减,区域间差距是空间非均衡的主要原因;公路密度空间极化程度不断增加,且高于铁路密度的极化程度;财政支出、国际贸易、人力资源和新经济地理四大因素对交通基础设施空间均衡和极化具有影响,但影响效果不同。本文拓展了交通基础设施的研究,为长江经济带交通基础设施协调发展及互联互通战略顺利实施提供了政策依据。     

SPATIAL ASYMMETRIC DUOPOLY WITH AN APPLICATION TO BRUSSELS' AIRPORTS*

ABSTRACT In this paper, the problem of a city with access to two firms or facilities (shopping malls, airports, commercial districts) selling a differentiated product (shopping, flights) and/or offering a differentiated workplace is studied. Transport connections to one facility are congested. A model is presented for this asymmetric duopoly game that can be solved for a Nash equilibrium in prices and wages. A comparative statics analysis is used to illustrate the properties of the equilibrium. A numerical model is then applied to the two Brussels airports. Three stylized policies are implemented to address the congestion problem: expansion of transport capacity, congestion pricing, and a direct subsidy to the uncongested facility. Our results indicate that the degree of intrinsic differentiation between the two firms is crucial in determining the difference in profit and market share. Price and wage differences also depend on trip frequency and consumer preferences for diversity. Congestion pricing is the most effective policy tool but all three options are shown to have attractive attributes.     

交通拥堵治理的空间与基础设施政策综述

交通拥堵是制约国内外城市可持续发展的瓶颈问题之一,给城市经济、社会与环境带来诸多负面影响.本文聚焦城市交通拥堵的结构性因素,系统归纳和综述了引导可持续出行行为的空间政策(如城市空间结构和土地利用政策)与基础设施供应侧政策(如道路和公共交通基础设施投资政策),及其在交通拥堵治理上的理论探讨、学术争论焦点、实证分析及当前亟...