Interregional labor migration and information flows

A model of interregional labor migration is developed that incorporates a complex system of information concerning migration and employment opportunities, as well as a heterogeneous population in which groups of workers differ in their assumed levels of skill, attitudes toward risk, and willingness to move. "Three channels are examined: interpersonal communication, general source information, and specific source information targeted at unemployed workers. In this process, trajectories of welfare levels (composed of wage plus nonwage benefits), information flows, vacancy and unemployment levels are generated for different worker and job types, regional aggregates, and the system as a whole. The behavior of the model is examined by means of numerical simulations and sensitivity analyses."     

Welfare payments and migration in a nonlinear,extended input-output model with an application to Scotland

This paper examines an extended input-output model that includes a migration mechanism and a locally funded welfare benefit regime. The model is developed to include two regions. Two different solution methods of the model are discussed, one involving the introduction of nonlinearities into the input-output framework. The results of the two solutions are compared using test data for a one-region formulation, and data for a two-region division of Scotland. The regional impacts of varying unemployment benefits differentially are assessed, and a range of impacts of economic and demographic regional injections presented.     

Multiregional estimation of gross internal migration flows

"A multiregional model of gross internal migration flows is presented in this article. The interdependence of economic factors across all regions is recognized by imposing a non-stochastic adding-up constraint that requires total inmigration to equal total outmigration in each time period. An iterated system estimation technique is used to obtain asymptotically consistent and efficient parameter estimates. The model is estimated for gross migration flows among the Canadian provinces over the period 1962-86 and then is used to examine the likelihood of a wash-out effect in net migration models. The results indicate that previous approaches that use net migration equations may not always be empirically justified."     

A model of trade flows in differentiated goods

In modelling trade competition for final products within a sector, the assumption of product homogeneity is often quite unrealistic. Even where the demand for different versions of the product can be attributed to relatively independent submarkets, considerable heterogeneity may still exist within each submarket. For each submarket, such as that for a medium-priced family car, it is assumed that more product heterogeneity exists between countries or regions than within them. Heterogeneity between regions is related to the existence of importers, acting as intermediate agents, who make trade-offs between cif import prices of goods and the willingness-to-pay by consumers. Aggregate spatial supply and demand functions based on plausible distributional assumptions are presented and estimated using a unified theoretical basis for each regional grouping of producers, importers and consumers. Conditions for simultaneous equilibrium for these three sets of agents are established, and illustrated via a small numerical example.     

A zero-inflated Poisson model of migration frequency

"This paper shows that the frequency of migration can be best modeled by a zero-inflated Poisson process, because it takes into account the overwhelming presence of zeros (nonmigrants) in the data. A failure to do so can cause the coefficients to be biased and also result in poor prediction. The major finding is that by using a zero-inflated process, the performance of the model in predicting migration behavior is substantially improved. In addition, frequent movers tend to be white, nonunionized, and tend to have fewer children, less stable marriages, and more frequent occupational changes." Data are for the United States for the years 1977 to 1987 and are taken from the Panel Study of Income Dynamics.     

Modelling migration flows of immigrant groups in Canada

"In this paper, the authors briefly review the findings of an earlier study on the patterns of both regional and metropolitan redistribution of immigrant groups in Canada. Against this backdrop, a hierarchical model of migration for immigrant groups for the period 1981-86 is developed and estimated. The internal redistribution of immigrants through postarrival migration has continued to be focused on metropolitan areas in general and on Toronto, Vancouver, and Montreal in particular. The distribution of previous immigrants plays a significant role over and above that of economic circumstances both in retaining immigrants in a particular city and in attracting members of immigrant groups from other cities."     

A model of reaeration rates driven by shear flows

The reaeration rate determines the speed that the dissolved oxygen is restored to the saturation level. The reaeration rate is determined by the surface renewal rates from the friction interfaces in the water bodies, including the water/bed interface, the shear‐flow interface and the air/water interface. The formulae of reaeration rate for the air/water interface and the water/bed interface were developed in prior studies. However, no formula of the reaeration rate driven by the shear flows was developed. In this study, a mechanic model of the reaeration rate driven by the shear flows is developed to fill in the gap. The flow velocity profile in the shear flows and the Surface Renewal Theory are employed to derive the corresponding model. The predictions of the formulae for these three types of friction interfaces are compared for the same phase velocity to investigate the reasonability of the reaeration rate model for the shear‐flow interface. The predictions of the model for the shear‐flow interface are between those for the air/water interface and for the water/bed interface. The model in this study is also verified to have reasonable agreements with the experimental data. The model developed in this study can be applied for the prediction of the low soluble gases’ transfer rate between air and water in shear flows.     

Inferring migration flows from the migration propensities of infants: Mexico and Indonesia

The need for methods of indirectly estimating migration flows is particularly important in developing countries, where migration data are often incomplete and inaccurate. This paper focuses on the use of an indirect internal migration estimation method applied to Mexican and Indonesian census data. It shows that the mobility propensities of infants can be used to infer the corresponding propensities of all other age groups. However, the promise of this method is reduced in instances of inadequate data, and great care must be taken to identify outlying values in the data and to correct obviously erroneous patterns. Future work increasingly will be directed to this issue.     

走中国特色城镇化道路

全面建设小康社会和逐步实现现代化,从根本上解决农业和农民问题,是中国现代化的难点。解决这个问题,在围绕“农”字做文章的同时,也要注重在“农”字以外做文章,“功夫在农外”。“三农”问题要从工业化、城镇化和市场化找出路。要通过“三化”促进“三农”问题的解决,也就是说,用先进技术改造农业和整个农村经济,通过城镇化实现大量农村人口向非农产业转移,坚持社会主义市场经济方向的改革,把农村经济纳入全国统一的市场化和社会化的轨道。　　我们是在特殊的历史背景下快速推进工业化的。20世纪80年代中期以来,随着政策逐步放宽,城镇…     

Poisson regression models of Canadian census division migration flows

Tax-file data are available for moves between census divisions in Canada on a year-by-year basis, and may be the best data source for studying migration flows between censuses. This paper reports the results of fitting a series of models to the 1985 to 1986 flows using a form of regression analysis based on the Poisson distribution that is appropriate for count data. These models confirm results well-known from interprovincial and intermetropolitan migration analysis, but also reveal some more surprising results.     

Estimation of place-to-place migration flows from net migration totals: a minimum information approach

"A truism in demography has been that net migration may be derived from information on gross place-to-place flows, but that gross place-to-place flows cannot be inferred back from information on the net population movements in a system. Some recent work on maximum entropy and minimum information models, however, suggests a possible means for estimating just such as set of place-to-place flows. The net migration constrained model presented here could prove particularly useful for updating detailed migration matrices on the basis of current net migration estimates, and could even provide some clues as to the nature of the still poorly understood relationship between gross and net migration. Performance of the model is demonstrated using flow matrices from the 1960 and 1970 U.S. Censuses.     

Development aspects of migration in third world settings: a simulation,with implications for urbanization

A simulation of the interrelationships between development and migration in developing countries is presented. "Development is represented as the diffusion of demographic transition, employment opportunities, and formal and communication channels, which in turn affect informal communications and the overall economic base. The simulation falls within the genre of neoclassical development models, but, unlike many, explicitly explores the long-run aspects of landscape evolution." The results generally "conform with expectations hypothesized in earlier research, including phenomena such as polarization reversal, converging regional disparities, and low-level equilibrium traps at small remote places where continual resource drain thwarts the agglomeration economies necessary for sustained growth. [The authors] also find that the initial urban system configuration has little effect on the final configuration, and that only urban size diseconomies are likely to alter significantly the size, spatial distribution, and spatial characteristics of the urban system."     

An alternative model for evaluating sustainable urbanization

In recent years, there has been rapid urbanization worldwide, resulting in both benefits and problems. Sustainable urbanization has become an important aspect in promoting sustainable development. Existing studies have introduced various methodologies to guide urbanization towards sustainable practices. The application of these methods has contributed to improving urban sustainability. To further support the effective applications of the principles of sustainable urbanization, a tool is needed to evaluate whether a particular process of urbanization is sustainable. In this paper, we introduce an alternative model for evaluating sustainable urbanization by investigating the relationship between urbanization and urban sustainability. The practice of sustainable urbanization is defined as a dynamic process that enables urban sustainability to improve or to maintain a certain level of practice. By employing this definition, we introduce a sustainable urbanization elasticity coefficient e_SU, which is defined by two parameters: urbanization velocity (V_μR) and urban sustainability velocity (V_μS). The sustainability of an urbanization process is measured by the value of e_SU or read from the V_μR-V_μS coordinate. A case study demonstrates the application of the measure e_SU and the V_μR-V_μS coordinate. The proposed model is an effective tool to help policy makers understand whether the urbanization processes they support are sustainable and thus whether to correct practices. The model also allows comparison of different urbanization practices and thereby encourages the sharing of successful experiences.     

A three-dimensional approach to multistream migration modelling: local-level flows in Hereford and Worcester

Using data for the English county of Hereford and Worcester, the author presents a method for the analysis of migration at the local level "which does not disaggregate migrant flows by distance criteria alone, but incorporates measures relating to the nature of the origins and of the destinations." The author suggests that "in comparison with a standard single-stream regression model this method improves the fit substantially, and the variability in the resulting parameter estimates for each of the eight streams supports the need for identification of distinct migrant streams. In particular, flows over short distances between wards with high population densities are estimated more effectively."     

Age articulation of U.S. inter-metropolitan migration flows

A fundamental divide in migration research has existed between aggregate studies of movement among geographic regions and micro studies of individual migrant behavior. Micro-scale studies have highlighted the importance of stage of life-cycle in predicting movement propensities, whereas many aggregate studies have focused on age-aggregated data summed over all origins for in-migration and over all destinations for out-migration. In this paper we show that if data for functional metropolitan-centered regions are employed, and if origin-destination specific streams of movement are analyzed, the age-specific patterns of inter-metropolitan migration within the United States cluster into distinctive patterns of flow representative of key stages of the life-course. In order to expose and portray a rich, age-articulated geography of U.S. migration we aggregate county-to-county migration flow data from the 1990 census for extended metropolitan regions: Bureau of Economic Analysis (BEA) Economic Areas. We calculate destination-specific out-migration rates broken down into 17 age groups for each origin-destination-specific migration stream between pairs of Economic Areas and present the results of a factor analysis of these flow-specific age profiles. We use the factor scores to cluster the very large number of origin-destination-specific age profiles and find that seven characteristic types emerge reflecting key mobility stages of the life course. We analyze the distinctive characteristics of the migration flows in each cluster and based on the prevalence of flows of each type within streams of gross in- and gross out-migration we present a typology of the 172 BEA Economic Areas. Our conclusion is that better understanding the age articulation of origin-destination-specific flow patterns would help advance regional science migration research. Received: January 2001/Accepted: June 2002 Earlier versions of this paper were presented at the 47^th North American Meetings of the Regional Science Association International, Chicago, Illinois, USA, November 9–12, 2000 and at the 12^th International Symposium Hosted by the Executive Secretariat of the Pacific Regional Science Conference Organization, Tokyo, Japan, October 1–3, 2000. The authors thank Joseph Persky, Roger Bolton, Hiroyuki Shibusawa, and Roger Stough for helpful suggestions made at those two presentations. The authors gratefully acknowledge the expert computer programming assistance of Lucy M. Carruthers of the Center for Computing and Information Technology of the University of Arizona. We also thank Chris Henrie, Ph.D. student, University of Arizona, for constructing our base map of BEA Economic Areas. Frank Heins would like to thank the National Research Council of Italy (Short-term Mobility Program 1999) for financially supporting a stay at the Department of Geography and Regional Development, University of Arizona. During his stay the groundwork for this research was laid. David Plane would like to acknowledge the support of the Population Division, U.S. Census Bureau for his 2001–2002 academic year visiting research position during which the final analyses and revisions were made.     

A parametric failure time model of international return migration

International return migration is conceptualized and modeled as the outcome of two opposing forces: assimilation into the host society and attachment to the home country. Assimilation is a cumulative learning process that, over time, lowers the tendency to return; attachment levels are less predictable: they might decrease, increase, or remain constant over time. From this proposition, we derive a generalized gamma function for the probability density function of the duration of stay, allowing for increasing, decreasing, and constant hazards of return. The applicability of the model is explored using the case of foreign migrants returning to their home countries from West Germany.     

一种新的岩石非线性流变损伤模型研究

传统岩石流变模型由线性元件组合而成,不能很好地描述流变过程中的加速流变阶段,通过分析岩石流变过程中微裂纹的压闭和扩展过程,将损伤力学引入岩石流变模型中,采用Kachanov提出的损伤律,将岩石流变过程分为阶段一（衰减、稳态蠕变阶段）和阶段二（加速蠕变阶段）两个部分,推导了岩石在两阶段中损伤演化方程,通过参数敏感性分析发现应力水平的大小对损伤演化过程有较大影响。结合有效应力观点建立了岩石非线性损伤流变模型,该模型能较好的描述岩石的衰减、稳态和加速流变阶段,同时简要分析了模型的松弛特性。采用该岩石非线性损伤流变模型对泥岩在围压为5 MPa与轴向偏应力水平为43 MPa的蠕变试验结果进行了模拟,验证了损伤流变模型的合理性,保持其他参数不变,更改应力水平的大小,得到不同应力水平下的非线性损伤蠕变模型曲线,与试验结果较为相符,