THE GROWTH AND DECLINE OF AMERICAN CENTRAL CITIES

The relative impacts of net migration, annexation and natural increase on central city population change are examined for the 118 largest American central cities. Region, central city age, and population size are also included as exogenous variables in the causal model. Annexation is found to offset some losses due to migration in older cities, but it is natural increase of the population that ensures continued central city growth or reduces the probability of decline.     

Population forecasting with endogenous migration: an application to trans-Tasman migration

"This article focuses on forecasting migration between Australia and New Zealand (trans-Tasman migration), which is largely visa-free and therefore resembles internal migration. Net trans-Tasman migration is a major component of New Zealand population change and is embedded in this article in a Bayesian or unrestricted vector autoregression (VAR) model, which includes foreign and domestic economic variables. When time series of net migration are available, this approach provides a useful input into forecasting population growth in the short run in the absence of major policy changes. This conclusion applies equally to interregional migration and to unrestricted international migration between economically integrated nations."     

Regional econometric model comparisons: What do they mean?

Accuracy comparisons among substate regional econometric models are becoming a standard part of the regional modeling literature. The comparisons typically are made without regard to area-specific economic/demographic structural differences and area-specific variations in data scope and quality. Since we have no background for evaluating the importance of these regional-based accuracy determinants, it is difficult to interpret the comparisons in terms of methodological improvement. By maintaining a consistent modeling methodology and a consistent time horizon in construction of models for six diverse areas, this study identifies and analyzes area-specific factors affecting substate model accuracy. Particularly critical factors are found to be distribution of population change between net migration and natural increase, two-digit distribution of manufacturing employment, sectoral firm concentration, economic/demographic growth pattern, consistency of data and availability of sectorally-specialized data. Differences across areas in these structural factors are seen to affect major sector MAPEs by factors of two to six leading to the conclusion that scientific analysis of methodological improvement in substate econometric models is unlikely to be achieved by interarea model comparisons.Financial support for this research was provided by the U.S. Department of Labor. The author accepts sole responsibility for content.     

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.     

Mobility Analysis

Mobility analysis is described as a technique more useful in small area demography than traditional methods which rely on concepts of natural increase and net migration. The proposed model relates to observations that in the absence of new housing construction, local populations are likely to decrease. The advantages of traditional analysis in dealing with development of age distributions are preserved.     

Migration in an interregional macroeconometric model of the United States: will net outmigration from the Northeast continue?

"This paper reports on the specification, estimation and simulation of an interregional net migration model of the United States. The model makes use of time series data including, as explanatory variables, wage rates, unemployment rates, and population density. Simulation experiments are undertaken by joining the migration model with a multi-regional macroeconometric model to examine the effect [on] migration patterns of changes in national economic growth. In particular, the net outmigration trends in the Northeast are examined under alternative scenarios including faster national economic growth and a different energy pricing policy."     

Interurban migration and the dynamics of a system of cities: 1. The stochastic framework with an application to the French urban system

"A stochastic framework for the modelling of interurban migration is presented. The model is an extension of a recently developed master-equation approach to interregional migration. The population dynamics of the French urban system, described by a set of 78 cities, is investigated within the period 1954-82. The importance of synergy effects (self-reinforcing collective effects) as well as socioeconomic macrovariables for the understanding of urban dynamics becomes obvious. A forecasting of urban dynamics...[up to the year 2002 confirms] this result and [gives] further insight into the nested structure of urban systems."     

组合预测模型在建筑结构寿命预测中的应用研究

着重对BP神经网络模型和组合预测模型进行了介绍,以“误差之平方和最小”作为最优准则,利用组合预测模型对回归模型和BP神经网络模型进行优化,通过对某混凝土结构剩余寿命的实例分析,检验了这些模型的可行性、可靠性。     

Short-term forecasting of internal migration

A new methodological approach to the forecasting of short-term trends in internal migration in the United States is introduced. "Panel-data (or longitudinal-data) models are used to represent the relationship between destination-specific out-migration and several explanatory variables. The introduction of this methodology into the migration literature is possible because of some new and improved databases developed by the U.S. Bureau of the Census.... Data from the Bureau of Economic Analysis are used to investigate the incorporation of exogenous factors as variables in the model." The exogenous factors considered include employment and unemployment, income, population size of state, and distance between states. The author concludes that "when one...includes additional parameters that are estimable in longitudinal-data models, it turns out that there is little additional information in the exogenous factors that is useful for forecasting."     

基于就业岗位的城市总体规划人口规模预测初探 ——以重庆市长寿城市总体规划为例*

快速城镇化进程中,城市发展的不确定因素越来越多,现有的以人口自然增长率和机械增长率为基本变量的总体规划人口规模预测方法已经难以适应这一客观趋势。针对人口的超常规增长,本文以重庆市长寿区中心城区人口预测为例,从常住人口产生的本质动因入手,提出基于就业岗位的人口预测方法,并对长寿区中心城区的人口进行了预测。     

Forecasting state and local population growth with limited data: the use of employment-migration relationships and trends in vital rates

In this study, the rate of growth of state and local populations in the United States is related to the growth rate of national employment, and to demographic and economic features of the regions concerned, in order to make more realistic long-term population projections. Both natural increase and migration are taken into account in the model developed. "The model is estimated for two regions, the El Paso, TX, standard metropolitan statistical area (SMSA) and the State of New Mexico. Several statistical problems arise because of the limited number of available time-series observations. Fully dynamic historical simulations track the population quite closely, in one case never differing from the actual value by more than 1.17% and in the other never differing by more than 1.36%."     

单桩极限承载力非等步长灰色GM（1，1）模型预测精度分析

分析了GM（1,1）模型与静荷载试验确定极限承载力的不同之处,指出了原有GM（1,1）模型极限承载力预测精度检验方法的不足,提出了新的符合静荷载试验加载特点的精度检验方法。对于不同类型的Q-S曲线,分析了初始建模数据的选择对GM（1,1）模型极限承载力预测精度的影响,并由此提出了初始建模数据选取的方法。     

A model of urbanization with nonlinear migration flows

"This paper seeks an appropriate specification of the migration exchange between rural and urban areas so that the implied evolution of the degree of urbanization agrees with its commonly observed S-shape. After demonstrating that the gross migration flows between rural and urban areas should be specified as nonlinear functions of the population in the origin sector, the paper introduces a model in which such flows are represented by gravity-type functional forms....[The model] can be used to give insights into the time paths of three basic urbanization variables: the urban-rural growth rate differential, the rural net outmigration rate, and the urban net immigration rate. All take on a zero value at the two extremes of the urbanization process and evolve in between according to a bell-shaped curve. These findings are illustrated by applying the model to data from the United States for the period 1790-1980."     

新陈代谢GM（1,1）模型在河流水质预测中的应用

针对常规GM(1,1)模型存在的不足,运用灰色系统理论,建立了灰色新陈代谢GM(1,1)河流水质预测模型,对该模型的精度以及误差进行了分析,并利用该模型对某地区河流的水质进行了预测,预测结果显示:灰色新陈代谢GM(1,1)预测模型能够明显地提高预测精度,增加预测的可信度。     

Migration cost externality and interregional equilibrium

This paper introduces the concept of migration cost in analyzing the interregional allocation of population. Migration cost gives the social planner an additional burden of population reallocation, and it has an important effect upon an individual's decisions on migration in a decentralized market mechanism. Interregional migration is influenced by migration cost, initial state of the population, etc. Though the difference of marginal productivity of labor and the consumption of composite good in one region is greater than that in another region, migration will not be desirable if the difference of net benefit between two regions from migration does not cover migration cost. Therefore, there will be a range of initial population allocation for which no migration occurs, not only for the social planner's problem but also for the individual's migration decision. Comparison of populations between social optimum and market equilibrium with central government intervention revealsmigration cost externality. The reason and remedy for this externality are discussed.     

Analysis of gross migration profiles in England and Wales: some developments in classification

"In this paper [the authors] describe the development and application of two approaches to the analysis of age and sex specific interarea migration. The data relate to local authority areas in England and Wales. These approaches are developments of established migration profile-fitting and cluster analytic methods. The paper shows how these methods have been used to develop complementary classifications from which potentially valuable criteria for migration analysis can emerge. The work described is part of a wider project concerned with the development of methods to improve the official estimation of internal migration in England in the context of local area population forecasting."     

Migration and urban change

"This paper examines the population development of large urban regions. Several hypotheses about patterns of settlement change in highly urbanized countries are discussed using empirical material derived from IIASA's Comparative Migration and Settlement Study. These hypotheses refer to interrelations between population growth and urban size, the role of migration and natural increase as components of urban population change, overall spatial mobility, hierarchical migration, and the age distribution of migrants moving between, out of, and into large urban areas." The emphasis is on developed countries. (summary in FRE, ITA, JPN, )     

The effect of basic employment and regional factors on net migration: A study for Washington state

Relationships between net migration and basic employment, income, and regional urbanization are examined using 1960–70 census data for the state of Washington. Regression analysis indicates that changes in employment in agriculture, forestry, fishing and mining and in manufacturing have a direct effect on the rate of net migration. Change in median family income is also directly related to net migration but the effect is not as strong as that of employment. Location by region has a substantial impact on net population shifts with net inflows attributable to the urbanization which occurred in western Washington from 1960 to 1970. The employment, income, and regional effects are clarified by explicitly recognizing rapid growth in educational, governmental and retirement activity and recent large increases in basic employment which occurred in two small groups of counties. Overall, the results indicate that while the rate of net migration is responsive to changes in basic employment and family income, it is also important to recognize regional factors such as urbanization.A special note of appreciation is expressed to Mr. Sharif Masud who developed background data used in the analysis. Work was conducted under Regional Project W-118 of the Agricultural Research Center, Washington State University.