60年来中国人口惯性变化及趋势

本文使用国际上较为成熟的测量方法,系统地计算了60年来中国总人口惯性、城乡人口惯性和分年龄人口惯性的变化和趋势。得出重要结论:第一,中国人口正增长的人口惯性作用正在逐渐消失;第二,中国城镇处于人口正负惯性的转折点,而中国人口的惯性增长完全来自农村;第三,中国人口惯性增长将突出表现为老年组人口规模大幅度的增长。     

21世纪中国人口负增长惯性初探

本文计算了中国1950～2006年期间的人口内在自然增长率,发现早在1990年时内在增长率就已经由正变负。并且通过该指标与人口自然增长率的比较发现,中国过去十几年的低生育率正在逐渐累积起人口负增长惯性。此外,本文基于不同的模拟方案结果揭示出,人口负增长惯性将会对未来中国人口规模和年龄结构有重大影响。本研究旨在说明,中国人口发展处于转折的关键时期,应当充分认识低生育率下的人口负增长惯性问题,有关人口决策必须尊重人口发展的内在规律。     

Family Benefits and Fertility: An Econometric Analysis

A population's growth potential is significantly underestimated by conventional calculations of population momentum which assume an immediate drop to replacement level fertility. Here we assume that the growth rate of births linearly declines to zero over a specified time interval, and find simple and intuitively meaningful expressions for the size of the ultimate birth cohort and the resultant population momentum. In particular, we find that the increase in the number of births over the transition is equal to growth at the initial rate for half the time needed to attain a constant birth level. Thus our formula readily calculates the growth potential of a population under a gradual approach to stationarity without the need for a numerical projection. Calculations for actual and hypothetical populations are presented to show the demographic impact of such gradual approaches to zero growth.     

The momentum of mortality change

Mortality change is not usually assigned much importance as a source of population growth when future population trends are discussed. Yet it can make a significant contribution to population momentum. In populations that have experienced mortality change, cohort survivorship will continue varying for some time even if period mortality rates become constant. This continuing change in cohort survivorship can create a significant degree of mortality-induced population change, a process we call the ‘momentum of mortality change’. The momentum of mortality change can be estimated by taking the ratio of e ₀ (the period life expectancy at birth) to CAL (the cross-sectional average length of life) for a given year. In industrialized nations, the momentum of mortality change can attenuate the negative effect on population growth of declining fertility or sustained below-replacement fertility. In India, where population momentum has a value of 1.436, the momentum of mortality change is the greatest contributor to its value.     

The family planning law should be issued as soon as possible]

China is facing a baby boom in the next ten years. Now is a perfect time to formulate legislature on family planning (FP) to strengthen the current policy and regulations in order to slow the momentum of excessive population growth. As a result of current economic reform and implementation of the rural household responsibility system, the migrant population has increased tremendously. The fact that millions of rural farmers are shifting to non-agricultural areas created new challenges to the effectiveness of traditional measures of the FP program. Promulgating laws and legislature will facilitate the job of FP. The law should stress the restriction of population growth and encouraging one child per couple. In the rural area it is not feasible to implement the one child policy indiscriminately. Under the policy of one child for a majority of the couples, no third birth is permitted. Local governments should be given the authorization to grant permission for second births for special cases within the birth planning quota. Allowing people living in poor and less developed areas to have more children and granting mothers of handicapped children permission to have an additional child were in fact facilitating the deterioration of the quality of the population. Some current policy in rural income distribution and social welfare was beneficial to large-sized family. Such policies should be changed to give incentives to small-sized families.     

入世对中国农村社会保障制度的影响

入世对我国农村社会保障制度的影响既有积极因素又有消极因素,总体而言是挑战大于机遇。     

人口惯性的测量方法

本文详细介绍了国际上较为成熟、可操作的人口惯性测量方法，包括人口内在自然增长率、人口惯性因子计算法、人口模拟预测法、以及年龄别人口惯性因子计算法；并分析了这些方法的优势和不足。同时，首次提出利用模型生命表和模型稳定人口，探索在人口数据缺乏的情况下，估算人口惯性大小，为从不同层面估计、量化人口惯性提供有效、实用的工具。     

Population momentum for gradual demographic transitions

Population momentum is the ratio of a population's ultimate size after a demographic transition to its initial size before the transition. For an instantaneous drop to replacement fertility, Nathan Keyfitz found a simple expression M K for the momentum. However, as Keyfitz pointed out, `no one thinks that any country will drop immediately to stationary reproduction patterns'. We present results concerning the momentum of a population whose demographic transition is completed within a finite time. First, we provide an exact analytical formula for such a population's momentum. Second, for rapid fertility transitions, we obtain a simple exact expression for momentum that reduces to Keyfitz's M K if the transition is instantaneous. We show, by example, that our simpler formulae are accurate approximations to population momentum for transitions that take as long as 100 years. Finally, we show that the speed of fertility decline makes a substantial difference to population momentum.     

Zero growth of the population of the United States

It is sometimes said that there is no population problem in the United States because the U.S. fertility rate is approximately at the replacement level of 2.1 children per woman. However the population of the United States increased in 1992 by approximately three million people. There are two major causes of continued population growth even when fertility is approximately at the replacement level. One is population momentum; the other is immigration. This paper examines what must be done if we want to achieve zero growth of the population of the United States immediately, without the long delays caused by population momentum.     

健全农村社会保障制度的思考

当前中国正处于深刻的社会转型之中,适应社会转型我们提出了在本世纪头20年建设惠及十亿人口的小康社会宏伟目标,而实现这一目标的重点和难点就在农村。现阶段制约中国农村全面建设小康社会的因素就是各地农村经济社会发展呈现出明显的差异性和不平衡性以及由此产生的社会保障相对滞后。为此,必须要大力加强农村社会保障制度的建立与完善,为全面建设小康社会保驾护航。     

Restructuring of the US Meat Processing Industry and New Hispanic Migrant Destinations

Findings from the 2000 US Census indicate high rates of Hispanic population increase beyond urban areas and traditional immigrant‐receiving states. The diversity of new destinations raises questions about forces attracting migrants to rural areas and links between economic structural change and Hispanic population growth. Our conceptual framework applies dual labor market theory to the meat processing industry, a sector whose growing Hispanic labor force offers an illustrative case study for analyzing how labor demand influences demographic change. We document the industry's consolidation, concentration, increased demand for low‐skilled labor, and changing labor force composition over three decades. We then position meat processing within a broader analysis that models nonmetropolitan county Hispanic population growth between 1980 and 2000 as a function of changes in industrial sector employment share and nonmetro county economic and demographic indicators. We find that growth in meat processing employment exhibits the largest positive coefficient increase in nonmetro Hispanic population growth over two decades and the largest impact of all sectors by 2000.     

The momentum of mortality change

Mortality change is not usually assigned much importance as a source of population growth when future population trends are discussed. Yet it can make a significant contribution to population momentum. In populations that have experienced mortality change, cohort survivorship will continue varying for some time even if period mortality rates become constant. This continuing change in cohort survivorship can create a significant degree of mortality-induced population change, a process we call the 'momentum of mortality change'. The momentum of mortality change can be estimated by taking the ratio of e0 (the period life expectancy at birth) to CAL (the cross-sectional average length of life) for a given year. In industrialized nations, the momentum of mortality change can attenuate the negative effect on population growth of declining fertility or sustained below-replacement fertility. In India, where population momentum has a value of 1.436, the momentum of mortality change is the greatest contributor to its value.     

Population momentum across the demographic transition

Population momentum is the main driver of global population growth today, and this makes an appreciation of momentum critical to understanding contemporary worldwide growth dynamics. This article traces population momentum along with two recently defined measures of momentum decomposed—stable and nonstable momentum—across the demographic transition. We use historical data and population projections from 16 countries to illustrate some previously ignored empirical regularities of the demographic transition in both the developed and the developing world. We also demonstrate the dynamic nature of stable and nonstable momentum, as changes in stable momentum lead to predictable changes in current and future nonstable momentum. These results suggest that momentum, which by definition is measured at a point in time, can also be considered as a process that unfolds over time.     

Future population growth: researchers in three countries quantify causes and propose policies

This article discusses Population Council analyses conducted by social scientists from India, Kenya, and the Philippines. These scientists agreed that population momentum would continue to increase population size, and that governments must strengthen and create a range of economic, health, and social programs and policies to slow population growth. Multiple approaches will be needed. John Bongaarts is credited with being the first to identify the key role of population momentum and to decompose growth into unwanted fertility, high desired fertility, and population momentum. Unwanted fertility is responsible for about 19% of projected population growth in India, 26% in Kenya, and 16% in the Philippines. High wanted fertility accounts for 20% of future growth in India, 6% in Kenya, and 19% in the Philippines. Population momentum can account for under 50% or over 90% of growth. Unwanted fertility can be addressed by fulfilling unmet need and increasing knowledge of methods, reducing the fear of side effects and disapproval, and eliminating poor service. Family planning programs need to be strengthened and integrated with maternal and child health services. Preferred and actual family sizes can be reduced by lowering infant mortality by means of increasing infant and child health services and girls' educational attainment. Population momentum can be addressed by delaying age at marriage and childbearing through improving social conditions. Investments in human development through education, training, and income generation can create the conditions for slowing population growth. Countries should decompose population growth into its components of unwanted and high wanted fertility and population momentum as a means of distributing resources most effectively.     

小城镇建设：甘肃农村剩余劳动力转移的现实选择

目前,大量剩余劳动力滞留于农村,成了解决农业、农村、农民(三农)问题的核心.在加快发展小城镇的基础上,能否促进其再就业已成为我国农村改革成败的关键.本文通过对甘肃小城镇发展现状、以及农村剩余劳动力转移过程中出现的问题进行了分析,并进一步提出相应的对策和措施.     

流动人口计划生育工作指标体系与考核评估方式初探

流动人口计划生育工作是我国计划生育工作的两大难点之一。要提高流动人口计划生育管理水平,必须建立科学的指标体系来规范流动人口计生管理。本文结合实践,论述流动人口计生管理工作指标体系设置原则,统计口径,以及管理质量考核评估方法和内容。     

Modeling momentum in gradual demographic

The analysis of population momentum following a gradual decline in fertility to replacement level provides valuable insights into prospects for future population growth. Here, we extend recent work in the area by applying a new form of the quadratic hyperstable (QH) model, which relates exponentially changing fertility to the resultant exponentiated quadratic birth sequence. Modeling gradual transitions from an initial stable population to an ultimate stationary population indicates that such declines in fertility increase momentum by a product of two factors. The first factor is a previously noted continuation of stable growth for half the period of decline. The second is a not previously appreciated offsetting factor that reflects the interaction between the decline in fertility, the changing age pattern of fertility, and the changing age composition of the population. Numerical examples using both hypothetical and actual populations demonstrate that for declines of any length, the product of the two factors yields momentum values that closely agree with the results of population projections. The QH model can examine monotonic transitions between any two sets of constant vital rates. As a generalization of the fixed-rate stable model, it has great potential value in numerous areas of demographic analysis.     

人口偏好结构转变、人口质量红利与农业发展：以中国东部地区为例

由工业化、城市化引致的农村人口偏好结构转变加速农业发展模式转变,农村人力资本水平提升为农业由人口数量红利型向人口质量红利型发展带来新的契机。作为内地经济最发达的东部地区在农村人口偏好结构正在发生转变的背景下,人力资本虽对农业增长具有正向作用但低于现代物质资本的贡献,东部地区农业发展仍依赖物质资本红利。随着工业化和城市化的持续推进,农村人口质量偏好进一步得到强化,东部地区将率先实现人口质量红利型农业发展模式。     

Population Trends in Metropolitan and Nonmetropolitan America: Selective Deconcentration and the Rural Rebound

This study uses revised annual population estimates that incorporate adjustments from the 2000 Census to backcast demographic change for U.S. counties during the 1990s. These data are supplemented with new post-censal population estimates for 2001–2003. We use these data to examine demographic trends in the late 1990s and first years of the new century. Our findings are consistent with a model suggesting that a selective deconcentration of the U.S. population is underway. Our findings also confirm the occurrence of the rural rebound in the first half of the 1990s and a waning of this rebound in the late 1990s. Post-censal data also suggest a modest upturn in nonmetropolitan population growth rates in 2001–2003.     

Movement toward stability as a fundamental principle of population dynamics

Although convergence to stability is typically a complex and irregular process, the Kullback distance provides a measure that moves consistently to 0 as a population becomes stable. The roots of the Kullback distance are in information theory, but it is a meaningful demographic quantity. It reflects a population's log momentum, or the amount of growth built into a population's nonstable age distribution. The rate at which the Kullback distance moves toward 0 is neither constant nor monotonic. At any point in time, however, it decreases by the covariance between a population's age-specific growth rates and its log momentum. Although the present findings are couched in terms of movement toward stability, they are generally applicable because they relate to the behavior of any population at any instant. It is a fundamental principle of population dynamics that a population is always moving toward the stable population implied by its prevailing fertility and mortality rates, and that the extent of its movement is determined by the covariance between its age-specific growth and its log momentum.