生育率演变的生态学逻辑及人口增长的长期趋势

人口增长的长期过程一直是充满困惑与引发争论的话题,将人类复归到生态系统的普通成员,按照生态学逻辑构建一个由替代生育率内生引导、人口容量外生制约的人口增长新模型,以代替用具体社会经济因子解释短周期人口变动的传统思路,探讨生育率转变的一般模式及人口发展的长期趋势。工业革命以来,全球人口已经或正在经历着第一次、第二次生育率转变,全球生育率演变可以聚类为欧美、亚非拉、撒哈拉以南非洲和东亚四种区域模式;在计划生育政策的推动下,我国在短短的三十年内完整经历了两次生育率转变。极限替代生育率是生育率演变的长期目标,但当前已有一些国家跌破更替水平,这也许会成为各个国家的普遍经历,预示着人口容量约束的日益显性化;世界及主要国家的人口规模正在日益逼近其容量极限,并会在惯性驱动下突破容量限制,达到峰值后再以负增长方式趋近人口容量,同期的生育率也将向极限替代生育率递增复归。按趋势模拟世界和中国的可持续人口容量分别约为65亿人和12亿人。研究设计出测量人口增长惯性的新指标——人口增长惯性系数,它是生育率与实时替代生育率之比或出生率与死亡率之比,相比常用的人口惯性因子更为简便易行。     

Some aspects of the use of birth expectations data from sample surveys for population projections

The value of national sample survey data relating to birth expectations for projecting births is reassessed in the light of data limitations pointed out by Ryder and Westoff among others and of the methods of projection used by the United States Bureau of the Census. The annual level of fertility under the cohort-fertility projection method depends on the assumptions regarding completed fertility, about which the available survey data are fairly informative, and on the assumptions regarding the timing of births, about which the survey data tell us very little. Test calculations suggest that Ryder and Westoff have overstated the significance of timing relative to completed family size for the level of future births. We believe that the fall in the annual total fertility rate in the first half of the sixties is to be explained only in part by a general delay in childbearing; a moderate to substantial decrease in completed family size has also occurred. Analysis of the latest set of fertility projections of the Census Bureau also suggests that the assumptions about completed fertility are a much more important determinant of the level of future births than timing, both in the short and long term. Although the available expectations data cannot help in predicting short-term annual changes in fertility, they appear useful for making long-term projections of annual fertility. Expansion of the size, frequency, and content of the sample surveys and incorporation of parity and birth interval into the projection method may improve projections.     

A macrosimulation approach to the investigation of natural fertility

This paper is part of a long-term investigation known as the Mormon Historical Demography Project. It examines the capability of a simulation model, originally proposed by John Bongaarts (1976), to fit the natural fertility pattern which characterized the mid-nineteenth century Mormon population. Application of this model permits estimates to be made of the historical timing and age-incidence of fertility limitation. A sensitivity analysis of the model’s parameters demonstrates that simple changes in the model’s proximate determinants of fertility, excluding contraceptive practices, would be insufficientto account for later transition effects. Thus the results successfully capture the dynamics underlying the Mormon natural fertility pattern as well as offer a framework for future modeling of the transition away from natural fertility.     

Options for Fertility Policy Transition in China

This article compares five currently debated scenarios for fertility policy transition in China, in terms of their implications for future population growth and population aging, the proportions of elderly living alone, labor force trends, pension deficits, economic costs, the marriage squeeze, and other socioeconomic outcomes. Based on these comparative analyses, the author concludes that China needs to begin a gradual modification of its fertility policy as soon as possible. He proposes a three‐stage “soft‐landing” strategy for fertility policy transition: (1) a 7‐year initial smooth transition period; (2) from approximately 2014‐15 to 2032‐35 a universal two‐child policy combined with late childbearing in both rural and urban areas; (3) after 2032‐35 all Chinese citizens would be free to choose family size and fertility timing. This strategy will enable China to have much more favorable demographic conditions and socioeconomic outcomes, as compared to keeping the current policy unchanged.     

A method of estimating the time of marital fertility decline and associated parameters

Significant research attention has been given to historical patterns of marital fertility transitions in currently industrialized countries. Specifically, studies consider the time of the onset of fertility decline and its distribution among populations or population subgroups; the distribution of pre-decline parital fertility levels; and/or the rate of marital fertility decline. Analyses of pre-decline fertility level and its rate of decline, however, depend upon the procedure used to estimate the time of fertility decline. The Princeton European Fertility Project is the most prominent historical fertility study ever conducted. The procedure employed to estimate the timing parameter in these Princeton studies is described. An alternative statistical procedure is then proposed for detecting the onset of the transition from high to low marital fertility; the method may also be used to find the termination point of decline where the sequence of fertility variables is long enough. Both methods produce maximum likelihood least squares estimates, but the form proposed in the text has conceptual advantages.     

The Momentum of Real Population Under Linear Fertility Transition

Population momentum is the ratio of a population's ultimate size after a demographic transition to its initial size before the transition. For stable population and instantaneous drop to replacement fertility, Keyfitz found a simple formula for the momentum. Although Keyfitz's formula has been extended to cover gradual demographic transitions, the stable initial population, however, is still an obstacle to approaching reality. Using the solution of the Lotka equation with time-varying vital rates and extending it to negative values of time, exact and accurate formulae for the momentum of any initial population that undergoes a linear fertility transition are expressed. Examples using the data from the United Nations indicate that the accurate formula works well for the age structures that are far from stable such as the more and less developed regions, as well as that close to stable such as the least developed region.     

The adoption of fertility control on Mykonos, 1879-1959: stopping, spacing or both?

This abstract examines the timing and means of the fertility transition on the Greek island of Mykonos in the period 1879 to 1959. By combining the results of family reconstitution with oral evidence, an unusual insight into the pathways of the fertility transition of this island population is offered. The paper concludes by outlining a model of the adoption of fertility control, a model which sees the transition from high to low fertility as a transition from spacing to stopping, and from innovation of methods to innovation of ideas.     

流迁人口对广东省人口发展的替代效应

所谓替代迁移是指迁移人口对长期处于更替生育水平以下的人口,因人口自然减少而产生的替代效用。广东省不但是全国人口流动和迁移最活跃的省份,而且人口总和生育率已连续10年低于更替水平,进入低生育水平时期。本文实证分析广东省在无流动人口、保持峰值人口、维持峰值劳动年龄人口和潜在供养比最大值等条件下,流迁人口对总人口规模和结构的替代效应,认为适度替代流迁人口是解决长期维持低生育水平地区所产生的人口问题的有效途径。     

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.     

Below-replacement fertility in Thailand and its policy implications

The fertility transition in Thailand has been one of the most rapid among Asian countries that are yet to attain newly industrialized country status. In the early 1960s, the total fertility rate exceeded six births per woman; currently, it stands at 1.9 or slightly below replacement level. At present, it is hard to predict the future trend in fertility as this involves several factors that need much closer study, in particular, fertility preferences, changes in marriage patterns and the wider effects of the current economic crisis in Thailand. Rapid declines in fertility and mortality have had a profound effect on the age structure of the population, notably the increasing elderly proportion. Thailand now faces new challenges and priorities for population policy. Policy responses to concerns arising from below-replacement fertility will be much more complex and involve greater government activism, improved institutional capacities and more resources than in the past. This paper reviews the fertility transition in Thailand and looks at some consequences and policy implications of low fertility, with special reference to the family and the elderly population. National Statistical Office     

Deliberate control in a natural fertility population: Southern Sweden, 1766–1864

In this article, we analyze fertility control in a rural population characterized by natural fertility, using survival analysis on a longitudinal data set at the individual level combined with food prices. Landless and semilandless families responded strongly to short-term economic stress stemming from changes in prices. The fertility response, both to moderate and large changes in food prices, was the strongest within six months after prices changed in the fall, which means that the response was deliberate. People foresaw bad times and planned their fertility accordingly. The result highlights the importance of deliberate control of the timing of childbirth before the fertility transition, not in order to achieve a certain family size but, as in this case, to reduce the negative impacts of short-term economic stress.     

中国人口转变地区差异的聚类分析

运用聚类分析方法 ,从总和生育率、平均预期寿命和自然增长率三方面综合了我国 1990年各地区的人口状况 ,将各地区按人口转变完成程度的异同进行了归类 ,并与按生育率转变完成程度的地区划分进行对比。结果显示 ,两种地区类型划分有较大的一致性     

The evaluation of China's population policy]

China's population policy has had tremendous effects on the reduction of fertility. The impact of the population policy is manifested in the following aspects. 1) Reducing the size of the total population by 200 million in 17 years. If the population growth rate had remained at its 1970 level of 2.6/1000, the total population would have been 1.28 billion in 1987. 2) The implementation of the population policy accelerated the process of demographic transition. The mortality decline which began in the early 1950s initiated the demographic transition. The Fertility decline began after the birth control policy was implemented and shifted the transition to a low population growth stage even before the socioeconomic conditions which are considered to be the determinants of fertility decline appeared. The fertility decline, in turn, promoted the socioeconomic development of the country. 3) Solving the problem of food; feeding 21.6% of the world's population on 7.1% of the world's farm land is no easy task. The success of population control, no doubt, played an important role in lowering the population growth rate so that the growth of food production could keep pace with the needs of the population. 4) A decline in the dependency ratio is a favorable condition to socioeconomic development. China's dependency ratio of 59.7 is among the lowest in developing countries and is close to the level in developed countries. Therefore, more production output can be used in investment rather than consumption. 5) The fertility decline facilitated a balanced economic growth. The ratio of population growth as compared to the growth of major economic indicators should be considered an important issue in maintaining macroeconomic control. The population policy made it possible for economic growth to surpass population growth.     

What do we know about the timing of fertility transitions in europe?

The Princeton project on the decline of fertility in Europe (the European Fertility Project) suggested that this historical fertility transition occurred virtually simultaneously in a wide variety of economic and social environments. This finding has been cited widely as evidence for an innovation/diffusion view of fertility transitions. We demonstrate that the demographic methods used to date the fertility transition in Europe—primarily I_g, and (to a lesser extent) the Coale-Trussell M&m indices—may fail to detect the initial stages of a fertility transition and therefore cannot be used as the basis for strong statements about the timing of transitions. We review these measurement problems and their implications for the current understanding of the European fertility transition.     

Pensions and fertility: back to the roots

Fertility has long been declining in industrialised countries and the existence of public pension systems is considered as one of the causes. This paper provides detailed evidence on the mechanism by which a public pension system depresses fertility, based on historical data. Our theoretical framework highlights that the effect of a public pension system on fertility is ex ante ambiguous while its size is determined by the internal rate of return of the pension system. We identify an overall negative effect of the introduction of pension insurance on fertility using regional variation across 23 provinces of Imperial Germany in key variables of Bismarck’s pension system, which was introduced in Imperial Germany in 1891. The negative effect on fertility is robust to controlling for the traditional determinants of the first demographic transition as well as to other policy changes.     

The role of intergenerational transfers,land, and education in fertility transition in rural Kenya: the case of Nyeri district

This qualitative study reveals how population pressures, land availability, inheritance norms, and educational opportunities intertwine to influence fertility decline in rural Kenya. Focus group discussions with men and women whose childbearing occurred both before and after the onset of rapid, unexpected fertility transition in Nyeri, Kenya allowed individuals who actually participated in, or witnessed, the fertility transition to “voice” their perceptions as to the mechanisms underlying the transition. Findings suggest that, since land inheritance is a cultural norm, land scarcity and diminishing farm size often influence fertility decision-making and behavior via preferences for fewer children. Further, education does not appear to be the driving cause of fertility behavior change, but rather is adopted as a substitute for land inheritance when land resources are scarce. These findings have implications for our understanding of fertility behavior as well as for improving predictions of fertility transition in other rural sub-Saharan African contexts.     

Population momentum for gradual demographic transitions: an alternative approach

In this article, I derive a simple formula for approximating the ultimate size of a population that undergoes a gradual transition to replacement fertility. I model the fertility transition by specifying a linear frontier on the Lexis surface across which a change in fertility is instantaneous. Gradual transitions result from variations in the slope of this frontier. This framework can be used to reproduce and understand previous studies of population momentum and gradual transitions.     

中国人口迁移与生育率关系研究

本文利用2000年人口普查数据,考察了中国人口迁移与生育率的关系。通过比较农村本地人口、城市本地人口和流动迁移人口三个人口群体在生育率上的差异,并进行多元统计分析,结果表明,流动迁移对生育率有着非常显著影响,城市外来人口的生育率不仅显著低于农村本地人口,而且也低于城市本地人口;远期流迁人口的生育率要低于近期流迁人口的生育率。中国人口迁移与生育率的关系出现了与已有的迁移生育率理论的不一致。1990年代中国的迁移生育率发生了转变。     

Transition of the population reproduction pattern in China]

In the past 30 years, great changes have taken place in the reproduction pattern of the population in China. A historical pattern of a high birth rate and high death rate no longer exists. A new low birth rate and low death rate pattern has now become a reality. It is especially notable that China has realized this transition under the condition of a backward economy. Since 1949, the death rate has dropped rapidly because of advancements in medical care, a rise in the standard of living, and an improvement in public health. The change in fertility, however, is determined by the developing level of social productivity. As mankind has moved forward, population reproduction has gradually become a self-conscious activity. Fertility is increasingly determined by views on marriage and concepts of birth. China has successfully achieved a transition in fertility, and this has to be credited to China's progressive relations in social production and an excellent social system. In addition, practical efforts made by the political leadership, cooperation from the people, and popularization of ideological education on family planning have all contributed to a transition in China's fertility rate.