Dynamics of age- and size-structured populations in fluctuating environments: Applications of stochastic matrix models to natural populations

Recent developments of the theory of stochastic matrix modeling have made it possible to estimate general properties of age- and size-structured populations in fluctuating environments. However, applications of the theory to natural populations are still few. The empirical studies which have used stochastic matrix models are reviewed here to examine whether predictions made by the theory can be generally found in wild populations. The organisms studied include terrestrial grasses and herbs, a seaweed, a fish, a reptile, a deer and some marine invertebrates. In all the studies, the stochastic population growth rate (ln λ _s ) was no greater than the deterministic population growth rate determined using average vital rates, suggesting that the model based only on average vital rates may overestimate growth rates of populations in fluctuating environments. Factors affecting ln λ _s include the magnitude of variation in vital rates, probability distribution of random environments, fluctuation in different types of vital rates, covariances between vital rates, and autocorrelation between successive environments. However, comprehensive rules were hardly found through the comparisons of the empirical studies. Based on shortcomings of previous studies, I address some important subjects which should be examined in future studies.     

含迁移要素的区域人口随机预测方法及其应用--以浙江省宁波市为例

以宁波市为例,基于宁波市“六普”与“五普”数据,首先利用年龄别死亡率对同批次队列人口进行年龄移算,即人口留存分析,对比2010年的实际人口数和无迁移模式下的封闭人口数之差,进一步测算两次普查期间分性别、年龄别人口的净迁移量和净迁移率。然后,将迁移率与出生率和死亡率整合,构建多要素随机人口预测模型,预测宁波市未来人口变化趋势,并评估迁移、死亡、出生三要素对人口变动的弹性影响效果。结果表明：人口净迁入对宁波市人口总量变化影响最大,而低死亡率和低出生率是未来50年加剧宁波市人口老龄化的主要原因。未来50年内,劳动力人口净迁入对降低宁波市人口老年负担系数的作用有限。鼓励夫妇生育二孩,优化人才引进与落户机制,尽快建立起应对高龄社会的公共服务体系尤其是长期照护体系,应是宁波市人口政策改革的当务之急。     

Counting snowbirds: The importance of and the problems with estimating seasonal populations

Using the example of the seasonal population of ``snowbirds' that spend the winter in Arizona and other Sunbelt states, this paper examines the issues involved with estimating temporary populations. Specifically using the experience of ASU's ongoing research efforts on Arizona snowbirds, the paper discusses some of the problems associated with estimating a seasonal population – in particular: (1) defining the population under study and (2) developing effective procedures to collect information relating to the population. The concluding section emphasizes the growing national importance of temporary populations and the needs of both the public and private sector to have better information on both their size and characteristics.     

人口增长率与人口规模关系的实证研究——基于中国省际面板数据的分析

文章在内生经济理论的框架下推导了在一定条件下人口增长率与人口规模负相关的结论,同时基于1954年至2007年的数据,运用动态面板数据模型验证了人口增长率与人口规模负相关。文章的动态面板协整检验表明,我国人口规模每增加一亿,人口增长率将减少2.13‰,我国人口规模将会达到15.4亿的峰值,然后人口增长率出现负增长。最后文章的格兰杰因果检验也表明,人口规模的变化是人口增长率变化的格兰杰原因。     

Bayesian population reconstruction of female populations for less developed and more developed countries

We show that Bayesian population reconstruction, a recent method for estimating past populations by age, works for data of widely varying quality. Bayesian reconstruction simultaneously estimates age-specific population counts, fertility rates, mortality rates, and net international migration flows from fragmentary data, while formally accounting for measurement error. As inputs, Bayesian reconstruction uses initial bias-reduced estimates of standard demographic variables. We reconstruct the female populations of three countries: Laos, a country with little vital registration data where population estimation depends largely on surveys; Sri Lanka, a country with some vital registration data; and New Zealand, a country with a highly developed statistical system and good quality vital registration data. In addition, we extend the method to countries without censuses at regular intervals. We also use it to assess the consistency of results between model life tables and available census data, and hence to compare different model life table systems.     

Extinction risk assessment of declining wild populations: The case of the southern Bluefin Tuna

We estimate the extinction probability of a large and decreasing population, the southern bluefin tuna. This tuna was listed as critically endangered by the World Conservation Union (IUCN) in 1996. However, the absolute population size is still large and the extinction probability within the next half century is negligible if the recent population decline rate does not increase in the future. IUCN’s criterion with respect to the population decline rate should be linked to the absolute population size, if this is estimated. Several methods estimating the probability of extinction conclude that the southern bluefin tuna population will be below 500 mature individuals within the next 100 years and may be listed as vulnerable. These analyses suggest that extinction risk assessment is useful for management action for taxa that still have large population and are rapidly decreasing.     

大城市流动人口居住形态与居住空间变动机理——以上海闵行区为例

流动人口的居住空间与居住形态是体现流动人口生存与发展的重要标志。本文着重分析了闵行区流动人口居住的基本特征与空间分布,构建了流动人口在城市居住的滞留模式,全面剖析了不同尺度下流动人口的流动机理,揭示了流动人口空间转换的状态与时空特征,提出实现居住分布空间优化的基本对策。     

人口老龄化：进程模拟和政策机制分析

以人口老龄化系数分析为主线,对相关统计数据从生育率、死亡率、老龄化系数、跨期队列人口四个方面进行模拟分析,推算出中国人口老龄化进程在1976年开始出现;计划生育政策是老龄化进程加速的关键因素,并导致我国步入老龄化国家行列的时间提前了12年;面对老龄化和高龄化浪潮,应当实行由国家主导、社会与家庭广泛参与的多元化的老龄化应对举措。     

Time series analysis and stochastic forecasting: An econometric study of mortality and life expectancy

Methods for time series modeling of mortality and stochastic forecasting of life expectancies are explored, using Canadian data. Consideration is given first to alternative indexes of aggregate mortality. Age-sex group system models are then estimated. Issues in the forecasting of life expectancies are discussed and their quantitative implications investigated. Experimental stochastic forecasts are presented and discussed, based on nonparametric, partially parametric, and fully parametric methods, representing alternatives to the well known Lee-Carter method. Some thoughts are offered on the interpretation of historical data in generating future probability distributions, and on the treatment of demographic uncertainty in long-run policy planning. All correspondence to Frank T. Denton. This paper is a revised version of one presented at the Annual Congress of the European Society for Population Economics, Athens, Greece, June 2001. The underlying work was carried out as part of the SEDAP (Social and Economic Dimensions of an Aging Population) Research Program supported by the Social Sciences and Humanities Research Council of Canada, Statistics Canada and the Canadian Institute for Health Information. Ronald Lee provided comments that were very helpful in revising an earlier version of the paper. We thank him and participants at the ESPE session at which that version was presented. We thank also the Journal's anonymous referees. Responsible editor: Junsen Zhang.     

Life Tables with Covariates: Dynamic Model for Nonlinear Analysis of Longitudinal Data

ABSTRACT

Life table models based on nonlinear dynamics of risk factors are developed using stochastic differential Equations for individual changes and on the resulting Fokker-Planck equation to describe population changes. Central to the model is a microsimulation strategy developed as a numerical procedure to represent a mortality effect when analytic approaches are not applicable. The model is applied to the Framingham Heart Study 46-year follow-up data. Life table functions and projections of risk factors are calculated to demonstrate the nonlinear effects on observable quantities over time. A set of statistically significant nonlinear contributions to covariate dynamics is identified. Their synergistic effect on dynamics and use of them as “new” risk factors are discussed. An important advantage of this approach is the ability to study the effects of health interventions at the individual level. This is illustrated in several examples.     

Statistical analysis of occupancy rates for overdispersed populations by redistribution procedures: Application to the european corn borer EGG masses distribution

Summary Standard statistical analyses of distributions of individuals from contingency tables are generally invalid if the individuals are not distributed independently of each other. In this paper, we discuss a method of testing hypotheses about classification category occupancy rates for overdispersed population or for population whose individuals are distributed by groups rather than lonely. These methods are based on population redistribution simulations and provide valid, exact and powerful tests in situations for which classical methods are not appropriate. Illustrations are given from the European Corn Borer eggs data.     

人际关系网络对农村劳动力转移的影响——基于工作搜寻模型的案例研究

杰克林·威波(JacklineWahba)和伊维斯·泽诺(YvesZenou)(以下简称为威波—泽诺)指出,求职者获得工作的成功率取决于他们所拥有的人际关系网络的规模和质量。本文利用威波—泽诺模型及河北省邯郸市11个县的基本数据,对人际关系网络与劳动力跨省输出的关系进行了回归分析,并在此基础上指出了这一模型的局限性。     

Dynamics of distribution in animal communities: Theory and analysis

Summary Theoretical and analytical problems of the dynamics of distribution and abundance in animal communities were examined. In many communities, species with low abundance and of limited spatial occurrence (i.e., rare species) typically form a conspicuous peak when a frequency distribution of the number of species is constructed with respect to the proportion of sites occupied within an area of distribution. Models of distribution dynamics, including a new model proposed here, were compared with a range of animal community data using a new procedure to assess single- and bi-modal patterns in frequency distributions of spatial occurrence. Data reveal that single-modality with an excess of rare species occurs more frequently than bimodality. Even when bimodality is detected, the mode representing wide-spread species is in the majority of cases smaller than that for rare species. Thus, a new model in which the rate of local extinctions is assumed to be negatively related to patch occupancy (or population abundance) is in better agreement with observed data than earlier models. Some problems of analysis, in particular model assumptions and testing, are discussed.     

The impact of delayed maternity on foetal growth in Spain: An assessment by population attributable fraction

Background

Delayed childbearing is considered a risk factor for maternal–foetal health. As in other higher-income countries, in Spain age at maternity has steadily increased during the last two decades.

Life table analysis of the green rice leafhopper,Nephotettix virescens (distant) (Hemiptera: Cicadellidae), and efficient vector of rice tungro disease in asynchronous rice fields in Indonesia

Summary Population dynamics ofNephotettix virescens was studied in 17 paddy fields transplanted at intervals of about 1 month in 1988–1990. The adult density was highest either in the immigrant or the 1st generation and sharply decreased to the 2nd generation. The survival rate of the 1st generation was lowest in the transition season when areal population density increased. Key factor analysis revealed that the nymphal and adult mortality of the 1st generation (kn) was the principal source of population fluctuations. No significant correaltion was found between kn and natural enemy density, natural enemy density/healthy egg density, or the precipitation during the nymphal period. On these bases adult emigration was suspected to be the key factor. Areal population build-up ofN. virescens in the transition season was considered to occur as a result of increasing immigration to young stages of rice. Contribution from Indonesia-Japan Joint Program on Food Crop Protection (ATA 162), which was implemented by the Directorate of Food Crop Protection, Ministry of Agriculture, Indonesia and Japan International Cooperation Agency, Japan.