Simulating urban population density with a gravity-based model

Theoretical justifications for the negative exponential urban density function were first proposed by urban economists, although some of their foundations have been criticized. From the geographer's perspective, the gravity-based model reported in this research uses a well-known concept (the “potential”) to offer an alternative explanation. Using numerical analysis techniques, the model simulates various urban density patterns. By varying the model's parameters (the distance friction coefficient β and the city size), the numerical simulations do confirm two important empirical findings: the flattening of density gradients over time owing to transportation improvements, and flatter gradients in larger cities. The observed relationship between the β value and the urban density gradient, as established by this research, opens an avenue for empirical testing.     

A switching regression analysis of urban population densities

An application of the switching regression technique in the field of urban economics is presented. The technique is applied to the study of urban population density functions, which recent research has suggested are inherently discontinuous. The method of switching regression developed by Quandt is used to estimate density functions for selected U.S. urban areas. The results show that population density contours are highly irregular, and also that the model selection approach can be used to select the number of regimes in a switching model when this number is unknown     

Wage gradients,rent gradients,and the price elasticity of demand for housing: An empirical investigation

As developed in Muth's “Cities and Housing,” attainment of locational equilibrium within an urban area implies a necessary functional correspondence between wage and price gradients and the compensated price elasticity of demand for housing. In this paper estimates of the rent and wage gradients are utilized to generate price-elasticity estimates via this equilibrium correspondence. The Box-Cox transformation technique is used with data from the metropolitan Chicago area to test for the functional forms of the wage and rent gradients. The optimal maximum-likelihood functional forms for both gradients yield a price-elasticity estimate of ?0.40.     

How good are two-point estimates of urban density gradients and central densities?

Some researchers have estimated urban density gradients and central densities using only information on the population and area of the inner city and the outer ring of suburbs. The statistical properties of these two-point estimates have not been previously analyzed. This paper shows the difficulties in providing a definitive analysis of these properties and provides, as an alternative, some Monte Carlo experiments. It appears that the two-point density gradients are mildly biased downward (toward zero), while the bias on the central density depends on the underlying error structure. Two-point estimates are compared with OLS and nonlinear least-squares estimates. Some results for actual cities are also provided.     

Urban residential density and income

Spatial variations in income have not been adequately accounted for in urban density regressions. Estimating equations incorporating household income are derived in a monocentric urban model. The technique used also yields an estimate of the income elasticity of demand for housing, found to be less than one.     

The density gradient for manufacturing industry

This study employs a rich set of disaggregated manufacturing industry data to estimate density gradients for five metropolitan areas over the time span 1967–1971. The results are consistent with both expectations and with a number of other studies of industry location. More importantly, however, this study examines many of the methodological problems associated with the density gradient. It is concluded that the density gradient has reached the point of diminishing returns as a tool of the urban economist.     

Measuring the value of urban amenities

This paper develops a model for estimating price gradients for several urban amenities that departs from traditional techniques. The approach used is both intuitively appealing and fully consistent with basic urban location theory developed over the past decade. Multidimensional price gradients are estimated for such amenities as low crime, clean air, accessibility to work, the local quality of education and local taxes. In addition subgroup analysis allows the comparison of the estimated “shadow prices” for two different income groups.     

我国城市基础设施产权制度的变迁

以制度变迁、产权和公共品理论研究为基础,通过对我国城市基础设施产权结构变革的原因和过程进行分析,提出我国城市基础设施产权制度变迁的基本路径,并指出这种制度变迁在客观上解决了我国城市基础设施长期以来的供给不足和效率低下等问题。     

城市生活方式变化与土地利用

本文基于城市社会学的视角,通过理论假设、调查问卷和构建结构方程模型实证等方法,研究了北京、上海、深圳、广州四个城市新移民的自身价值观、生活方式和城市土地利用的关系。分析结果表明,移入城市生活的居民其自身价值观会有所改变,价值观的改变对生活方式、城市土地利用行为产生了正向的影响,生活方式与城市土地利用密切关联。因此,本文认为增加公共政策的人本关怀和正向引导积极的城市生活方式,对于优化城市土地利用结构至关重要。     

Urban density and pupil attainment

We explore the association between urban density and pupil attainment using three cohorts of pupils in schooling in England. Although—as widely recognised—attainment in dense urban places is low on average, this is not because urban environments disadvantage pupils, but because the most disadvantaged pupils with low average attainments attend the most urbanised schools. To control for this, we exploit changes in urban density faced by pupils during compulsory transition from Primary to Secondary school, and measure educational progress at the end of the Secondary phase, relative to attainment at the end of Primary schooling. Our results suggest that there are small but significant benefits from education in schools in more densely urbanised settings. We detect this density advantage even amongst pupils moving relatively short distances between Primary and Secondary schools within urban areas, so we cannot attribute it to broad urbanisation effects experienced by pupils making rural–urban school moves. A more likely explanation lies in greater school choice and competition between closely co-located educational providers.     

Estimation and recent behavior of urban population and employment density gradients

The monocentric model of urban structure predicts that urban population density declines with distance from the central business district. Using the negative exponential function to approximate the decline, Mills (E. S. Mills, “Studies in the Structure of the Urban Economy,” Johns Hopkins Press, Baltimore, Md. (1972)) estimated population and employment density gradients from 1948 to 1963 for a sample of 18 SMSAs. This paper updates Mills' estimates and examines recent patterns in population and employment suburbanization. The updated series estimated here is obtained using a “corrected” version of Mills' method. The original procedure incorporated a bias which Mills noted and later corrected (E. Mills and K. Ohta, in “Asia's New Giant” (Patrick and Rosovsky, Eds.), The Brookings Institution, Washington, D.C. (1976)). The comparability of the series begun by Mills and extended here is not interrupted, however, because, as Mills suspected, the bias is indeed small provided SMSA data are used. On the other hand, Urbanized Area definitions of metropolitan areas cause the original and corrected versions to yield significantly different results. This finding has implications for the appropriate choice of data for urban studies.     

Auto pollution and congestion in an urban model: An analysis of alternative strategies

Congestion and pollution externalities associated with automobile driving are examined for their effect on urban structure. A monocentric urban model which incorporates household preferences for both an unpolluted environment and for leisure time is presented, and used to evaluate alternative pricing and emissions policies on automobile use and their effects on city structure. Optimal tax gradients for driving are derived, and compared with second best cases of per mile taxes and no taxes. As externalities gradients become more nonlinear, the welfare gains from employing optimal taxes rather than a per mile tax are increased. The appropriate choices of an emission standard, highway capacity, and highway pricing policy must be made simultaneously and depend on household preferences.     

Econometric issues in interpreting Mills' estimates of urban density gradients

Mills has estimated a first order, autoregressive distributed lag model of the process of adaptation of urban density gradients. The error term in such equations estimated by ordinary least squares is likely autocorrelated, biasing upward the estimated coefficient of the lagged dependent variable. A specification error may be concealed, with autocorrelation in the error term resulting in overestimates of the length of the adjusted lag. Longer time series samples will be required if the nature of the lagged adjustment processes and the error term are to be simultaneously estimated.     

中国城乡二元体制的形成及其变革

城市化是中国社会的发展趋势,统筹城乡发展是中国未来几十年的工作重点和经济社会发展动力.路径依赖和制度规模效应固化了城乡二元结构;要实现城乡一体化必须实行制度变迁,具体而言要基于城乡公民享受平等的政治权利、迁移自由权利、教育权利、社会保障权利、土地财产权利,加强制度创新.     

An empirical investigation of intraurban wage gradients

Intraurban wage gradients have received little attention in the urban literature but have been shown theoretically to be important indicators of the spatial characteristics of urban economic activity. This study examines the spatial distribution of wages of five groups of municipal public employees in the Chicago SMSA. Negative wage gradients, significant at the 0.05 level, are found for four of the five labor groups. Results show that monthly wages decrease on average as much as $24 per additional mile from the city center.     

Are compact cities environmentally friendly?

There is a wide consensus among international institutions and national governments in favor of compact (i.e. densely populated) cities as a way to improve the ecological performance of the transport system. Indeed, when both the intercity and intra-urban distributions of activities are given, a higher population density makes cities more environmentally friendly because the average commuting length is reduced. However, when we account for the possible relocation of activities within and between cities in response to a higher population density, the latter may cease to hold. Indeed, an increasing-density policy affects prices, wages and land rents, which in turn incentivizes firms and households to change place. This reshapes the urban system in a way that may generate a higher level of pollution. Thus, although an increase in compactness is environmentally desirable when locations are given, compactness may not be environmentally-friendly when one accounts for the general equilibrium effects generated by such a policy.     

城市空间生产过程中的社会排斥

城市空间不仅是物理空间,也具有一定的社会属性。中国的社会变迁在城市空间生产过程中留下了深刻的烙印,从建国初期的较为均等的城市空间分配到改革开放后的城市空间分异,都体现了当时的社会管理体制、社会关系结构及其变迁。分析了变迁过程中存在的基于结构和个体层面的双重空间社会排斥,并指出这两方面的排斥力造成了目前城市空间分异的现象。     

Congestion,agglomeration, and the structure of cities

Congestion costs in urban areas are significant and clearly represent a negative externality. Nonetheless, economists also recognize the production advantages of urban density in the form of positive agglomeration externalities. The long-run equilibrium outcomes in economies with multiple correlated but offsetting externalities have yet to be fully explored in the literature. Therefore, I develop a spatial equilibrium model of urban structure that includes both congestion costs and agglomeration externalities. I then estimate the structural parameters of the model using a computational algorithm to match the spatial distribution of employment, population, land use, land rents, and commute times in the data. Policy simulations based on the estimates suggest that congestion pricing may have ambiguous consequences for economic welfare.     

南京市的城市土地集约利用的探讨

随着我国城市化建设的快速发展,城市化进程中的土地资源利用也产生了很大的变化。在我国,城市化进程过程中的土地利用扰对非常剧烈,主要表现在城市用地总量及结构失衡的生态恶化。本篇文章对城市化进程中的南京城市土地集约利用展开讨论,结合南京土地集约利用的状况,提出了相关的政策建议。     

城市用地结构与产业结构关联的实证研究——以重庆市为例

城市用地结构与产业结构的有机耦合是提高城市用地效益,促进产业结构高级化和城市整体功能提升的前提和保障。文章利用比例变化指数和Granger因果法对重庆市城市用地结构和产业结构耦合关系的实证研究显示:重庆市城市产业结构变化滞后于城市用地结构变化,城市用地结构变化与产业结构变化的差距呈现先上升后下降的趋势,即重庆市城市用地结构与产业结构的有机耦合在经历了非同步变化后逐渐步入同步变化的轨迹;短期内,城市用地结构变化推动产业结构的优化,随之,产业结构又反作用于城市用地结构;城市用地结构和产业结构同步变化轨迹还没有出现,这说明城市用地结构与产业结构互为因果的关系应在长期的调整、协调中才能得以实现。