北京市外来人口聚集区:模式和发展趋势

外来人口聚居区的出现和发展,是城市化进程中的产物,它已成为北京外来人口生活居住的主要地区。2000年,北京市外来人口上万人的街道有102个,占到街道总数的30.4%,集中居住了74.4%的外来人口。外来人口高度聚集的情况短期内不会消失,并会随着北京的发展,形成数量更多、规模更大的聚集区。聚集区可以按照内部结构划分为缘聚型和混居型,依照行业依托情况分为完全依托、半依托和无依托。从动态角度来看,社会实行最低工资限额并能让向上流动成为可能,无依托型外来人口聚集区或许会继续保持一段时间的中转功能之后,转型或消失。完全依托型和半依托型聚集区问题则只能从产业结构调整、市场分布及配套方面入手解决。     

An age‐structured model of population dynamics with dominant ages,delayed behavior,and oscillations

An age‐structured model of population dynamics with age‐dominance is proposed and analyzed. Existence and uniqueness of solutions are established as well as the uniqueness and local asymptotic stability of steady‐states. Conditions for convergence to or oscillation about the steady‐state are specified in some cases.     

Population dynamics and monetary policy

This paper shows that in a general equilibrium model with interest-rate feedback rules of the Taylor-type population dynamics give rise to multiple steady states. Under an active monetary policy, real determinacy occurs only around the steady state with zero net financial wealth, where aggregate consumption is equally distributed among agents of different generations. By contrast, in a neighborhood of the steady state displaying a positive stock of financial wealth and intergenerational inequality, real determinacy requires monetary policy to be passive. Changes in the demographic profile of the economy are shown to have relevant implications for the aggregate accumulation of wealth.

以人口健康观看我国健康保障制度改革

人口健康观是将健康的概念由个体健康拓展到以人口为基础的群体层面的一种新理念．它关注的是健康而不是疾病。从人口健康观看,我国健康保障制度改革存在着许多认识上的误区,应该以社区健康为中心重建健康保障制度。     

Turbulent dynamics in a Xviith century population

A reconstruction of the population of the Pays de Caux (1589–1700) yields the time series of a fertility behavior indicator, the overall Coale index If. In spite of the noisy appearance of its evolution, the trajectory of If looks ordered, as if it were confined alternatively to two given zones, looping in each of them for a while, then suddenly jumping from the low one to the higher one, or slowly whirling down from the high to the low one.

An attempt is made to explain this general temporal structure by using a simulation model based on the autoregulation model (the so‐called European Marriage Pattern), putting into play a choice of the spouse function, a fertility function, modalities of marriage and remarriage, under the environmental forcing of the reconstructed mortality conditions.

The correspondence between reconstruction and simulation turns out to be quite good, not only for the population size or the Coale index, but also for the marriage series, quite independently of the reconstructioa

A second simulation with simulated mortality conditions shows a bifurcation point: as the mean frequency of crisis increases, the state of the system leaves the lower level and concentrates more and more in the higher level.

Thus, not only does the autoregulator model appear validated by empirical data, but its bi‐modal structure is revealed, depicting the dynamic response of a traditional community both to the environment and to the endogeneous demographic process.     

人口“双龄化”背景下对我国养老保障制度建设方向调整的思考

我国人口发展呈现老龄化和高龄化的趋势,而人口的“双龄化”对社会养老保障提出了更高的要求,政府和社会不但要为老年人提供基本的养老金。而且还要提供高龄老人必要的老年服务;不但要着力保障“三无”、“五保”等特殊老人．而且还要关注占老年人口大多数的普通老人。从我国目前的社会保障建设看,基本养老金制度建设比较全面、系统,从制度设计层面覆盖了各种人群,而养老服务保障建设还显不足,尤其是面向广大普通老人的相关服务保障缺失。当前要加快养老保障制度建设转型。要以养老金制度为主向经济保障和服务保障制度并重的方向发展。服务保障对象应以特殊人群为主向特殊人群与普通人群并重的方向发展,应建立以政府引导、社会主办、民间参与的多层次养老服务保障体系。而社区服务保障具有经济性、便捷性及可及性等诸多优点．是广大普通老人获得养老服务保障的重要途径。     

Temporary migration: a case study of Florida

Most migration statistics in the United States focus on changes in permanent residence, thereby missing temporary moves such as the daily commute to work, business trips, vacations, and seasonal migration. In this paper, we analyze temporary migration streams in Florida, focusing on moves that include an extended stay. Using several types of survey data, we examine the characteristics of non-Floridians who spend part of the year in Florida and Floridians who spend part of the year elsewhere. We develop estimates of the number, timing, and duration of temporary moves and the origins, destinations, characteristics, and motivations of temporary migrants. This study presents the most comprehensive analysis yet of temporary migration in Florida and provides a model that can be used in other places. It also points to a serious shortcoming in the US statistical system, namely, the lack of information on temporary migration streams. We believe the American Community Survey provides an opportunity to remedy this problem.     

Explicating donor trends for population assistance

Using population assistance data, this study divides donor trends for population assistance into five distinct epochs: until the mid-1960s, the population hysteria of the 1960s and 1970s, Bucharest Conference and beyond, the 1984 Mexico City conference, and the 1990s. A number of decisive events, as well as changing views of the population problem, characterise each period and have affected the sums of population assistance from donor nations. Taking a long-term view of global population assistance, the research shows that four factors account for most of the historical funding trends from primary donors: the association between population assistance and foreign aid, the role of alarmists and doomsayers in the public debate over population issues, individuals in a position of power within donor governments, and decennial international population conferences.     

A general host–pathogen model with free–living infective stages and differing rates of uptake of the infective stages by infected and susceptible hosts

In addition to their lethal effects, pathogens can cause a number of other debilitating effects on infected hosts. A population dynamical model of the interaction between an invertebrate host and a pathogen is constructed to examine the importance of one such debilitating effect on the host population dynamics. Specifically the feeding rate and therefore the uptake of pathogen free-living infective particles by infected individuals is reduced as a consequence of the pathogen infection. The pathogen is more likely to regulate the host and the equilibrium population density of the host is reduced. Less intuitively there is also an increased chance of the pathogen causing cyclic population dynamics in the host. Received: December 8, 1997 / Accepted: March 23, 1999     

New techniques in small area population estimates by demographic characteristics

The increasing demand for small area population estimates calls for both innovative ways of using existing data and new techniques suitable for small area estimates. This paper explores the methods for population estimates by age, sex, race, and Hispanic origin at the census tract level for Multnomah County, Oregon. New techniques include employing building permits to indirectly estimate migration and examining the changes in age/sex structure using the American Community Survey (ACS). A practical method for bridging the race categories is also developed. Finally, the paper discusses some reflections on small area estimates and the potentials of using ACS to track the changes of the demographic characteristics for the sub-county level.     

The American Community Survey: general commentary on the findings from external evaluations

As part of the Census Bureau’s effort to prove the operational feasibility of the American Community Survey (ACS), the Bureau contracted with local experts to conduct comparative analyses of the 1999–2001 ACS estimates with the 2000 Census data for various test counties. One of the goals of the ACS is to replace the decennial census long form. The resulting research papers analyzed various quality measures (response rates, allocation rates, and so on), conceptual differences in the two instruments, and statistical reliability in an effort to add to our assessment of the ACS as an adequate replacement instrument for collecting long form data. This paper discusses the results of these four research efforts and presents conclusions and recommendations for further Census Bureau action and research. The quality of traditional long form data, the importance of accurate population estimates and an accurate Master Address File (MAF), and continued research on the quality of small area data are discussed.     

On the validity of MAPE as a measure of population forecast accuracy

The mean absolute percent error (MAPE) is the summary measure most often used for evaluating the accuracy of population forecasts. While MAPE has many desirable criteria, we argue from both normative and relative standpoints that the widespread practice of exclusively using it for evaluating population forecasts should be changed. Normatively, we argue that MAPE does not meet the criterion of validity because as a summary measure it overstates the error found in a population forecast. We base this argument on logical grounds and support it empirically, using a sample of population forecasts for counties. From a relative standpoint, we examine two alternatives to MAPE, both sharing with it, the important conceptual feature of using most of the information about error. These alternatives are symmetrical MAPE (SMAPE) and a class of measures known as M-estimators. The empirical evaluation suggests M-estimators do not overstate forecast error as much as either MAPE or SMAPE and are, therefore, more valid measures of accuracy. We consequently recommend incorporating M-estimators into the evaluation toolkit. Because M-estimators do not meet the desired criterion of interpretative ease as well as MAPE, we also suggest another approach that focuses on nonlinear transformations of the error distribution.     

An individual-based model for competingDrosophila populations

An individual-based model forDrosophila is formulated, based on competition amongst larvae consuming the same batch of food. The predictions of the model are supported by data for single speciesDrosophila populations reared in the laboratory. The model is used to build a simple discrete model for the dynamics ofDrosophila populations that are kept over a number of generations. The dynamics of a single species is shown to give either a stable equilibrium or fluctuations which can be periodic or chaotic. When the dynamics of a species in the absence of the other is periodic or chaotic, we found coexistence or two alternative states, on neither of which the species can coexist.     

温室效应:人口要负多大责任?

由于各国经济利益不一致,气候变化谈判博弈艰难。在这种形势下,人口控制对减少温室气体排放的意义,近来被国际社会部分人士及中国政府重新提及,值得关注。自1972年世界环境大会以来,发达国家对世界人口问题的看法发生过180度的转变,否认发展中国家人口快速增长对经济的不利作用,否认人口与环境问题相关的观点,渐成西方学术界主流,由学术界蔓延到西方政府,并深刻影响着发展中国家许多学者的认识。文章论述了人口规模对温室气体排放的影响,试分析了上述西方主流观点在研究方法上存在的问题。目前,中国正进入快速工业化阶段,对庞大人口不断放大的经济、资源、环境影响,本文认为必须有极为清醒的认识。     

城市可持续发展与人口安全——以上海为例

将安全意识纳入城市可持续发展战略,寻求人口与资源、环境、社会、经济系统的相互协调,实现共同安全和系统间的均衡发展已成为当前和未来城市管理的重要研究领域。本文以上海为例,从系统间视角分析了当前和未来人口发展过程中存在的安全隐患,并指出,人口与其它子系统的协调发展必须在相互适应、相互调节的过程中实现双向互动。     

A model on the escape from the Malthusian trap

We consider a demoeconomic model where output is produced using physical capital, human capital and technology as inputs. Human capital depends on the number of people and the level of education in the economy. The dynamics of labour, physical capital, education and technology are endogenously determined such as to reflect the interdependence between economic and demographic factors. The longrun path of the economy and in particular the possibility to escape the Malthusian trap crucially depend on technological progress, which provides for economy wide increasing returns to scale. The build up of technology is positively related to the stock of human capital. Our model predicts that positive population growth is sufficient to escape the Malthusian trap. Received: 22 August 1996 / Accepted: 11 December 1997     

Women's empowerment as a public problem: A case study of the 1994 International Conference on Population and Development

Using the 1994 International Conference on Population and Development (ICPD) as a case study, I examine how women's empowerment amassed public attention. I investigate feminist preparations for the conference and suggest that by playing an active role in preparatory meetings and the conference, women gained recognition from governments throughout the world and from the United Nations, and helped frame issues in a way that motivated the press to highlight women's empowerment. I argue empowering women became a catch phrase for media coverage and that abortion surfaced as a symbol of this empowerment. UN publications and reports of proceedings prior to, and during the 1994 ICPD, and articles from The New York Times illustrate use of this media package. The paper raises questions about types of policies governments will use to improve the position of women and the political power women will have in decisions.     

Human population as a dynamic factor in environmental degradation

The environmental consequences of increasing human population size are dynamic and nonlinear, not passive and linear. The role of feedbacks, thresholds, and synergies in the interaction of population size and the environment are reviewed here, with examples drawn from climate change, acid deposition, land use, soil degradation, and other global and regional environmental issues. The widely-assumed notion that environmental degradation grows in proportion to population size, assuming fixed per capita consumption and fixed modes of production, is shown to be overly optimistic. In particular, feedbacks, thresholds, and synergies generally amplify risk, causing degradation to grow disproportionally faster than growth in population size. Based on a presentation to the Bixby Symposium on Population and Conservation, UC Berkeley, May 2006.     

A population dynamic model of Batesian mimicry

Summary A population dynamic model of Batesian mimicry, in which populations of both model and mimetic species were considered, was analyzed. The probability of a predator catching prey on each encouter was assumed to depend on the frequency of the mimic. The change in population size of each species was considered to have two components, growth at the intrinsic growth rate and carrying capacity, and reduction by predation. For simplicity in the analyses, three assumptions were made concerning the carrying capacities of each population: (1) with no density effects on the mimic population growth rate; (2) with no density effects on the model species; and (3) with density effects on both species. The first and second cases were solved analytically, whereas the last was, for the most part, investigated numerically. Under assumption (1), two stable equilibria are possible, in which both species either coexist or go to extinction. Under assumption (2), there are also two stable equilibria possible, in which either only the mimic persists or both go to extinction. These results explain the field records of butterflies (Pachliopta aristolochiae and its mimicPapilio polytes) in the Ryukyu Islands, Japan.     

Density-dependent growth and reproduction of the apple snail, Pomacea canaliculata : a density manipulation experiment in a paddy field

To examine density dependence in the survival, growth, and reproduction of Pomacea canaliculata, we conducted an experiment in which snail densities were manipulated in a paddy field. We released paint-marked snails of 15–20 mm shell height into 12 enclosures (pens) of 16 m² at one of five densities – 8, 16, 32, 64, or 128 snails per pen. The survival rate of released snails was 95% and was independent of snail density. The snail density had a significant effect on the growth and egg production of individual snails. This density dependence may have been caused by reduced food availability. The females at high density deposited fewer and smaller egg masses than those at low density, and consequently produced fewer eggs. The females at densities 8 and 16 deposited more than 3000 eggs per female, while the females at density 128 oviposited only 414 eggs. The total egg production per pen was, however, higher at higher snail density. The survival rates of juvenile snails were 21%–37% and were independent of adult density. The juvenile density was positively correlated with the total egg production per pen and hence was higher at higher adult density. However, the density of juveniles larger than 5 mm in shell height, i.e., juveniles that can survive an overwintering period, was not significantly different among density treatments. These results suggest that snail density after the overwintering period is independent of the density in the previous year. Thus, density dependence in growth and reproduction might regulate the population of P. canaliculata in paddies. Received: October 23, 1998 / Accepted: July 16, 1999