中心-外围模型的错误和再求解-对克鲁格曼解法的质疑

本文对中心—外围模型的错误进行了研究,并运用角点均衡求解方法对模型进行了重新求解。结果显示,当制造业运输成本较高时,全部制造业集聚于中心地区;当运输成本较低时,经济系统均衡于对称专业化模式。这一结论与克鲁格曼的结论正好相反。之所以发生这种情况,是因为制造业运输成本是作为一种集聚力而出现的,只有当运输成本系数较高时,人们才会有动力聚集在一起,以减少相互之间的贸易和运输。随着该系数的下降,这种节约动机变得越来越微弱,并最终导致中心—外围结构瓦解。     

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.     

Ricardian Comparative Advantage and Geographical Concentration

This paper analyses geographical concentration using the continuum‐of‐goods trade model in the presence of labor migration, Ricardian comparative advantage and Marshallian‐type external increasing returns to scale. The findings show that higher transportation costs lead to concentration in one region, and lower transportation costs lead to diversification between the regions. For intermediate transportation costs, asymmetric diversification becomes a stable equilibrium in which the smaller population region has higher wage rates and a smaller externality, and vice versa. However, because the asymmetric equilibrium is an inefficient outcome, it leaves room for government intervention.     

A note on the Hotelling principle of minimum differentiation: Imitation and crowd

This paper investigates price competition in the Hotelling location model with linear transportation costs when consumer preferences are affected by the number of consumers shopping at the same store. A consumption externality permits us to consider the imitation and the congestion effects which are opposite forces at work. The coexistence of the two effects confers new validity to the principle of minimum differentiation as it was in the original Hotelling model. I show that firms do not need to set apart in order to earn higher profits. The results show firms endogenously choosing to locate in the center of the interval sharing the market with positive prices.     

The effect of distance and road quality on food collection, marketing margins, and traders' wages: evidence from the former Zaire

Food price variation is typical of the food economies of many low income countries. The presence or absence of road infrastructure is perceived to be one of the main determinants of this variation. This analysis shows that in the case of the former Zaire, food price dispersion is significant both across products and across regions. It is demonstrated that transportation costs explain most of the differences in food prices between producer regions and that road quality is an important factor in the transportation costs. However, food prices decrease relatively faster than transportation costs increase and traders' wages are higher on bad roads.     

A contraction principle for finite global games

I provide a new proof of uniqueness of equilibrium in a wide class of global games. I show that the joint best-response in these games is a contraction. The uniqueness result then follows as a corollary of the contraction principle. Furthermore, the contraction-mapping approach provides an intuition for why uniqueness arises: complementarities in games generate multiplicity of equilibria, but the global-games structure dampens complementarities so that only one equilibrium exists.     

专业化产业集聚、空间成本与区域工业化

本文扩展了贸易成本的范围,认为贸易成本不仅包括产品运输成本,而且也包括要素流动成本,并引入前后向产业联系,认为中间产品使用及种类的增加所创造的成本和需求联系效应有利于提高最终产品的生产效率。在此基础上文章发展了可解的中心-外围模型,并探讨了在各种条件下相应的经济学含义,认为在推动我国区域经济一体化的进程中,对落后地区的技术支持必不可少,重视区域间产业发展的互动,否则,我国区域经济一体化进程难以有效推进。     

Inter-Region Transportation Costs,Regional Economic Growth,and Disparities in China

To examine the correlation between regional economic growth and inter-region transportation costs in China, this study establishes a regional economic growth model embedded with inter-region transportation costs based on the Cobb-Douglas production function. Based on a balanced growth empirical model, this study verifies the correlation by conducting a regression analysis of the panel data of 29 provinces, municipalities, and autonomous regions from 1985 to 2015. The empirical results show that: (1) The per capita GDP growth among the three regions (namely, the eastern, central, and western regions of China) meets a conditional convergence trend, and the decreasing of the inter-region transportation costs increases the convergence speed; (2) The per capita GDP growth is in line with the club convergence trend within each of the three regions; (3) The trend of the output elasticity of the inter-region transportation costs shows that the gradual decrease of inter-region transportation costs has a positive correlation with the narrowing of economic disparity after the year 2000, accelerating "common prosperity" across different regions in China.     

On financial deepening and long-run growth

I develop a stylized model of endogenous growth in which the level of financial depth influences an economy’s long-run growth. Financial depth is defined within the model as the ease with which investors can issue equity in the market on new units of capital. I assume that agents differ in the cost of undertaking investment projects and that there is a fixed distribution of such costs across the population. I theoretically identify channels through which financial depth influences growth, both positively and negatively. When considering a specific distribution of costs, I show that the net effect of financial depth on growth is non-monotonic. It depends on the shape of the distribution, as well as the level or stage of financial depth. The results of this paper help to rationalize some findings in the recent empirical literature on the non-monotonic effect of financial depth on long-run growth. The model is even capable of obtaining a negative effect of excessive financial depth on growth, a result that is also found in the empirical literature.     

Commuters route choice behaviour

The paper reports laboratory experiments with a two route choice scenario. In each session 18 subjects had to choose between a main road M and a side road S. The capacity of M was larger. Feedback was given in treatment I only on the subjects' own travel time and in treatment II on travel time for M and S. The main results are as follows:

• Mean numbers on M and S are near to pure equilibrium.

• Fluctuations persist until the end of the sessions.

• The total number of changes is significantly greater in treatment I.

• Subjects' road changes and payoffs are negatively correlated.

• A direct response mode results in more changes for bad payoffs whereas a contrary response mode shows opposite reactions.

• Simulations of an extended payoff sum learning model fits the main results of the statistical evaluation of the data.

One-way flow networks: the role of heterogeneity

I study a one-way flow connections model in which players are heterogeneous with respect to values and the costs of establishing a link. I show that values and costs heterogeneity are equally important in determining the level of connectedness and the architecture of equilibrium networks. I also show that when asymmetries are independent of the potential partner there are distributions of costs and values for which centrality is a distincitive feature of equilibrium networks. This sharply contrasts with the homogeneous case.I thank an anonymous referee for useful comments. The paper has benefited from discussion with Gabriella Conti, Jose Luis Moraga-Gonzalez, Fernando Vega-Redondo and Sanjeev Goyal.     

专业化产业集聚、空间成本与区域工业化

本文扩展了贸易成本的范围，认为贸易成本不仅包括产品运输成本，而且也包括要素流动成本，并引入前后向产业联系，认为中间产品使用及种类的增加所创造的成本和需求联系效应有利于提高最终产品的生产效率。在此基础上文章发展了可解的中心一外围模型，并探讨了在各种条件下相应的经济学含义，认为在推动我国区域经济一体化的进程中，对落后地区的技术支持必不可少，重视区域间产业发展的互动，否则，我国区域经济一体化进程难以有效推进。     

Optimum city size: A minimum congestion cost approach

The optimal allocation of urban land between the generation of traffic and the carrying of traffic which minimizes congestion costs is derived for a circular city. Unlike previous work which dealt only with the suburbs, this paper deals with both the suburbs and the central business district. This wider view of the problem leads to different conclusions, the most important of which is the fact that at no point in the city is all the land used for transportation. Existence of a maximum size for a city of a given working population, which is independent of relative land and congestion costs, is also discussed with special reference to the case where there is no land rent.     

Engel's law, Petty's law, and agglomeration

This paper presents a model of structural change and agglomeration. A decline in transportation costs, by enhancing consumers’ purchasing power, leads to Engel's law of the demand shift from agricultural to non-agricultural goods. At the same time, the decline in transportation costs, by enlarging the extent of the market for non-agricultural goods, induces Petty's law of the labor reallocation from agriculture to non-agricultural activities. These structural transformations weaken dispersion forces given by farmers tied to the land, whereas they strengthen agglomeration forces generated by footloose non-agricultural workers. Thus, a substantial decline in transportation costs gives rise to agglomeration of non-agricultural activities.     

A QUANTITATIVE ANALYSIS OF SUBURBANIZATION AND THE DIFFUSION OF THE AUTOMOBILE*

Suburbanization in the United States between 1910 and 1970 was concurrent with the diffusion of the automobile. A circular city model is developed in order to access quantitatively the contribution of automobiles and rising incomes to suburbanization. The model incorporates a number of driving forces of suburbanization and car adoption, including falling automobile prices, rising real incomes, changing costs of traveling by car and with public transportation, and urban population growth. According to the model, 60% of postwar (1940–1970) suburbanization can be explained by these factors. Rising real incomes and falling automobile prices are shown to be the key drivers of suburbanization.     

TRANSPORTATION COSTS,AGRICULTURAL PRODUCTIVITY,AND CROSS‐COUNTRY INCOME DIFFERENCES*

I study the role of transportation for development by introducing regional trade and a transportation sector into the standard two‐sector model of agriculture–nonagriculture. Low transport productivity can distort the allocation of resources across geographically dispersed production units within sectors and between agriculture and nonagriculture. I infer cross‐country transport productivity disparities from observed domestic transport costs and transport infrastructure stocks. “Endowing” rich countries with the transport productivity of poor countries would reduce their income by 10%. Combining transport productivity disparities with disparities in nonagricultural productivity and arable land the model yields a 50% higher rich–poor income ratio than the two‐sector model.     

Projections of oil demand in road transportation sector on the basis of vehicle ownership projections,worldwide: 1972–2020

Oil demand in the road transportation section accounts for more than 50% of total world oil consumption amongst the whole sectors, including road, aviation, railway, waterways and international marine transportation. The high demand rate of oil makes this sector the main and major oil consumer in the world. The vehicle ownership or intensity of vehicles is one of the main factors which determines the development of oil demand in this major sector.Vehicle ownership (in 1000 population) is estimated using the nonlinear Gompertz model on the basis of pooled time series (1972–2020) and cross-sections data for 154 countries. Different saturation levels for the selected countries and over time horizon is calculated by adding specific demographic and geographic variables. Then, under two different scenarios – business as usual and policy scenario – we make projections of oil demand in the road transportation sector across 154 countries by using available data up to 2020.According to the results of the model, it is predicted that the number of world total vehicles will be approximately 1.5 times higher in 2020 than in 2008. Moreover, oil demand projections for road transportation over 2009–2020 show that under business as usual scenario, world oil demand will increase to 14,748 million barrel of oil equivalent until 2020 while under the policy scenario, which is based on the fuel efficiency improvement by 20% during a period of 10 years until 2020, world oil demand in the aforementioned sector will increase only to 11601 mboe until 2020.     

EXISTENCE AND UNIQUENESS OF EQUILIBRIUM FOR A SPATIAL MODEL OF SOCIAL INTERACTIONS*

We extend Beckmann's spatial model of social interactions to the case of a two‐dimensional spatial economy with a large class of utility functions, accessing costs, and space‐dependent amenities. We show that spatial equilibria derive from a potential functional. By proving the existence of a minimizer of the functional, we obtain that of spatial equilibrium. Under mild conditions on the primitives of the economy, the functional is shown to satisfy displacement convexity. Moreover, the strict displacement convexity of the functional ensures the uniqueness of equilibrium. Also, the spatial symmetry of equilibrium is derived from that of the primitives of the economy.     

Paving the Road to Export: Assessing the Trade Impact of Road Quality

Assessing the trade impacts of domestic transport costs is data demanding and analyses that examine the effects of road quality, a critical aspect in regional and public policy, practically do not exist in the international trade literature. The few studies available rely mostly on distance-based measures as proxies of transport costs which impede analyzing the trade effects of transport-infrastructure improvements. In this paper, we combine highly disaggregated records of export flows with detailed geo-referenced information of the Colombian transport network, including its road quality, as well as real measures of transport costs of shipping goods within the country to measure the trade impacts of improving road quality. We find that the trade effects of improvements in road quality are relatively small on average; however, there is considerable heterogeneity in the magnitude of the effects. We show that longer routes have larger shares of their roads in poor conditions; accordingly, the trade impacts of shipments originated in remote regions are found to be quite substantial.     

The core of some location games

An important problem in Location Theory is that of assigning plants to locations in an optimal manner. In the context of this problem, recognizing interplant transportation costs, Koopmans and Beckmann (1957) introduced the Quadratic Assignment Problem (QAP). It is shown in this paper that when the QAP is formulated as a cooperative location game, its core may be empty. By contrast, the core of the game corresponding to thelinear assignment problem (where transportation costs are disregarded) is assured to be non-empty. Some conditions under which the core is non-empty are discussed.I am grateful to two anonymous referees of this journal for their comments.