Changes In Age Structure Research Articles

Population economic function model based on data mining algorithm

Population structure changes interact with economic development, moderate population and reasonable population structure are important guarantees for sustainable social and economic development. The research ignores the specific impact of the change of population age structure on economic growth, and proposes and establishes a population economic function model based on data mining algorithm. Based on the changes of population structure in Liaoning Province in the past 20 years, Grey correlation analysis method is selected. The analysis shows that there is a close relationship between population structure and economic growth. Based on this research, the econometric method is used to construct a multiple linear regression model to further analyze the specific impact of population structure changes on economic growth. The analysis results show that the total population of urban areas, the total number of employed people in the primary industry, the number of middle school students per 10,000 people, and the total number of employed people in the tertiary industry are the four most significant demographic indicators for the per capita GDP of the study area. There is a significant positive correlation between the total number of employed people in the tertiary industry and per capita GDP and there is a significant negative correlation between the total number of employed people in the primary industry and the number of middle school students per capita and per capita GDP. The impact of other indicators on per capita GDP is not significant. According to the conclusion, countermeasures and suggestions to ease population structure change and promote the coordinated development of population and economy in the study area are put forward.

Population Exposure Projections to Intensified Summer Heat

AbstractPopulation aging, an increasing share of the elderly to the total population, can exacerbate heat vulnerability to intensified heat hazards. However, the aging impacts on increases in exposure of the elderly to unprecedented hot summers (UHSs) could be variable in the warming climate. Here, we present considerable contribution of age structure changes to increases in the elders' exposure to intensified UHSs in countries with a high percentage of youth population, namely, China, India, and Brazil, by analyzing combined scenarios of climate change with population structure. In the aforementioned regions, increases in exposure to stronger UHSs relevant to rapid aging will exceed at least half of the warming impact, which primarily causes frequent occurrence of stronger UHSs. Conversely, the United States and Europe, which have already entered an aged society, show a negligible aging impact. These results suggest that the future evolution of a society's age structure is an important constraint for projecting population exposure to strengthened summer heat.

Incorporating vital rates and harvest into stochastic population models to forecast elk population dynamics

AbstractThe dynamics of ungulate populations across variable ecosystems and management strategies demonstrate disparate trajectories such that some populations are overabundant, while other populations are subject to recovery efforts. Understanding how variation in vital rates such as pregnancy and survival integrate to shape the trajectories of populations is, therefore, helpful for informed management, particularly given that our understanding of the dynamics of harvested ungulate populations is often limited. Age‐related variation in vital rates among elk (Cervus canadensis) suggest that suitable population matrix models require age‐specific vital rates that can be logistically and analytically challenging to obtain. Our goals were to use a large, long‐term data set on elk and hierarchical Bayesian models to estimate age‐specific pregnancy and annual survival rates and their process variances, use stochastic population projection matrices to understand the effects of additional mortality from harvest on population dynamics, and identify the influence of different combinations of vital rates on population trajectories. We found that median age‐specific pregnancy rates increased with age from yearlings (0.52, 90% credible interval [CrI] = 0.37, 0.65) to a plateau among prime ages (e.g., 9‐year‐old: 0.91, 90% CrI = 0.87, 0.94), followed by a decline for the oldest ages (e.g., 19‐year‐old: 0.10, 90% CrI = 0.03, 0.28). Annual survival rates plateaued among prime‐aged animals (e.g., 9‐year‐old: 0.94, 90% CrI = 0.92, 0.96), and declined for the oldest‐ages (e.g., 19‐year‐old: 0.21, 90% CrI = 0.04, 0.56). We found higher process variation in pregnancy rates than survival rates; annual pregnancy rates for a 7‐year‐old varied from 0.82 (90% CrI = 0.67, 0.92) to 0.98 (90% CrI = 0.95, 0.99), and annual survival rates varied from 0.94 (90% CrI = 0.85, 0.96) to 0.96 (90% CrI = 0.93, 0.99). Simulated population trajectories indicated that additional mortality due to harvest resulted in a shift in the age structure towards younger animals with lower probabilities of pregnancy. When we held calf survival between 0.48 and 0.50 and specified constant pregnancy rates, changes in age structure alone resulted in variation of the recruitment of female calves from 0.20 to 0.16. We found that populations with a low mean value of calf survival (0.25) and no additional mortality due to harvest had marginal demographic performance ( = 1.02) and could sustain no additional mortality from harvest and still increase. In contrast, productive populations with a high mean value of calf survival (0.75) required high harvests to abate population growth (e.g., harvest rate = 0.20, = 0.94). Finally, we found a temporally lagged effect of harvest on age structure such that a shift towards younger animals could persist for multiple years following a reduction in harvest, suggesting that harvest may have multi‐year lagged depressive effects on population growth rates above and beyond the direct effects on survival rates. Our work highlights the importance of considering the effect of varying age‐structure on population dynamics, suggests minimum combinations of vital rates required for increasing or decreasing elk population growth rates to general management objectives, and provides the framework required for future management‐specific recommendations using stochastic population projection matrices.

Perioperative management of ortho-geriatric knee or hip arthroplasty patients

Due to the changing age structure of the Western population, an increase in geriatric patients in endoprosthetic care of hip and knee joints is to be expected in the future. The age-related frailty and the existing comorbidities pose great challenges for the entire treatment team. In the preoperative phase, geriatric patients should be identified as such and adjustable risk factors should be addressed prior to surgery. The primary goals of treatment are to minimize trauma from anesthesia and endoprosthetic surgery to ensure immediate postoperative mobilization of patients. At the same time, any perioperative complications, especially intensive care treatments, should be prevented. This is achieved excellently with algorithms that are well known from fast-track surgery.

Global urban temporal trends in fine particulate matter (PM2·5) and attributable health burdens: estimates from global datasets

SummaryBackgroundWith much of the world's population residing in urban areas, an understanding of air pollution exposures at the city level can inform mitigation approaches. Previous studies of global urban air pollution have not considered trends in air pollutant concentrations nor corresponding attributable mortality burdens. We aimed to estimate trends in fine particulate matter (PM2·5) concentrations and associated mortality for cities globally.MethodsWe use high-resolution annual average PM2·5 concentrations, epidemiologically derived concentration response functions, and country-level baseline disease rates to estimate population-weighted PM2·5 concentrations and attributable cause-specific mortality in 13 160 urban centres between the years 2000 and 2019.FindingsAlthough regional averages of urban PM2·5 concentrations decreased between the years 2000 and 2019, we found considerable heterogeneity in trends of PM2·5 concentrations between urban areas. Approximately 86% (2·5 billion inhabitants) of urban inhabitants lived in urban areas that exceeded WHO's 2005 guideline annual average PM2·5 (10 μg/m3), resulting in an excess of 1·8 million (95% CI 1·34 million–2·3 million) deaths in 2019. Regional averages of PM2·5-attributable deaths increased in all regions except for Europe and the Americas, driven by changes in population numbers, age structures, and disease rates. In some cities, PM2·5-attributable mortality increased despite decreases in PM2·5 concentrations, resulting from shifting age distributions and rates of non-communicable disease.InterpretationOur study showed that, between the years 2000 and 2019, most of the world's urban population lived in areas with unhealthy levels of PM2·5, leading to substantial contributions to non-communicable disease burdens. Our results highlight that avoiding the large public health burden from urban PM2·5 will require strategies that reduce exposure through emissions mitigation, as well as strategies that reduce vulnerability to PM2·5 by improving overall public health.FundingNASA, Wellcome Trust.

The life quality of the disabled as a result of diseases of peripheral nervous system

The article considers results of studying the quality of life of disabled patients because of diseases of peripheral nervous system. The significantly low level of indices of quality of life self-assessment was established on all scales of SF-36 questionnaire that are from 3 to 7 times lower than similar indices in population of Russia. The assessment of quality of life of disabled patients is necessary to determine effectiveness of applied rehabilitation measures and application of obtained results in planning further rehabilitation and habilitation activities.

Demographic dividend in Saudi Arabia: From age structural changes to economic gains

Aim/purpose – The demographic dividend, defined as the proportion of working age to the rest of the population, is an opportunity seen mainly in developing countries, result- ing from demographic transition. Efforts to maximize gains from it are crucial, especial- ly for the Arabian Gulf states, where labor force demands are met at the danger of native youth unemployment that leads to issues of human resources utilization. This research on Saudi Arabian demographic dividend aims at tracking changes in the age structure, labor force participation, and prospects leading to economic gains. Design/methodology/approach – Data from various sources such as censuses (1974, 1992, 2004, and 2010), national labor force surveys 1999-2017 and United Nations (UN) Population Prospects are compiled and statistically analyzed with a historical approach for calculations of age distribution, median age, and labor force participation adopting standard procedures. Findings – An age structural transition occurred: percentage of population 15-64 years increased from 47.2% to 67.3%, increasing the dividend from 89.6% to 205.5%. This influenced the labor force’s sectoral distribution, and Gross Domestic Product (GDP) per working age population. Research implications/limitations – The dividend’s first phase, since 2000, is expected to last until 2050, followed by the second dividend which may last longer. Along with the dividend, there shall be policies executed to reap the benefits, including scientifically planned recruitment of potential candidates in various professions, both in public and private sectors. Originality/value/contribution – This research concerns a population, which is unex- plored in detail, especially at a macro level. Thus, such an in-depth analysis seeks im- portance in revealing special demographic dimensions to a wider international audience. There are no such studies conducted in Saudi Arabia, with a national perspective helpful for revamping efforts to boost labor force reforms and to make maximum gain during the short-lived demographic dividend period. Keywords: demographic transition, accounting effect, age-sex structure, labor force, median age. JEL Classification: B55, J10.

Young Lads and Old Tars: Changing Age Structure of the Nordic Sailors, 1750s–1930s

AbstractThis article analyzes the changing age structure of Swedish and Finnish sailors for almost 200 years. We show that the proportion of the youngest men increased during the age of sail (i.e., the older technology). The average age increased significantly during the early twentieth century as steam (i.e., the newer technology) replaced sail in Nordic shipping. Thus, a technological revolution did not displace the older workers, but rather diminished the demand for the younger ones. This study shows, however, that technological changes were not the only drivers of changes in the age structure of Nordic sailors. Institutional and societal changes also played an important role, though they were at least partly coevolving with the technological changes. This study also shows that the maritime industry experienced professionalization especially during the latter part of the period.

云龙天池国家级保护区云南松种群年龄结构及动态分析

PDF HTML阅读 XML下载 导出引用 引用提醒 云龙天池国家级保护区云南松种群年龄结构及动态分析 DOI: 10.5846/stxb202105081208 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 云南省教育厅科学研究基金项目（2020Y0017）；国家自然科学基金项目（31660118）；中国植被志（针叶林卷）编研 Age structure and dynamics of Pinus yunnanensis population in Yunlong Tianchi Nature Reserve Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:云南松是中国西南地区的特有树种。云南松林是暖温性针叶林的典型代表，主要分布于滇中高原。云南松种群是否可以自我更新，将影响滇中地区的植被动态。明晰未受干扰的云南松种群的结构和动态是研究云南松林可持续发展的重要基础。云南省云龙天池自然保护区内的云南松林是较为原始的森林。以云龙天池国家级自然保护区云南松天然种群为研究对象，分析了云南松天然种群静态生命表、存活曲线、生存函数曲线和谱分析。结果表明：云龙天池国家级自然保护区的云南松年龄结构为倒J型，种群年龄结构数量变化动态指数Vpi为28.29%，存在外部干扰时侯的种群年龄结构动态指数V'pi为1.77%，种群动态指数Vpi和V'pi都大于0，种群在外部环境干扰下承担的风险概率Pmax为6.25%，以上结果表明云南松种群为增长型种群结构，具有一定的抗干扰能力。云南松种群的存活曲线为Deevey-Ⅱ型，生存分析发现生存率、累计死亡率、死亡密度和危险率在Ⅰ-Ⅶ龄级（胸径<35 cm）变化较大，Ⅶ-XVI龄级（胸径35-80 cm）趋于稳定；谱分析结果表明第Ⅲ龄级（胸径10-15 cm）是影响种群数量的主要阶段。以上结果说明云南松种群的低龄级个体数量波动大，个体死亡较多，高龄级衰退，建议自然保护区内的天然云南松幼龄林和中龄林可以采取抚育间伐措施来促进其种群的生长发育和更新。 Abstract:Pinus yunnanensis is an endemic tree species in Southwest China. P. yunnanensis forest is a typical representative of warm coniferous forest, mainly distributed in the central Yunnan plateau. Whether P. yunnanensis populations can self-renew or not will affect the vegetation dynamics in central Yunnan. Clarifying the structure and dynamics of undisturbed P. yunnanensis populations is an important basis for studying the sustainable development of P. yunnanensis forests. The P. yunnanensis forest in the Yunlong Tianchi Nature Reserve in Yunnan Province is a relatively pristine forest without human interference. In this study, the static life table, survival curve, survival function curve and spectral analysis of P. yunnanensis natural populations were analyzed in Yunlong Tianchi Nature Reserve. The results demonstrated that the age structure of P. yunnanensis in Yunlong Tianchi National Nature Reserve was inverted J-type, the dynamic index of population age structure change in quantity Vpi was 28.29%, the dynamic index of population age structure in the presence of external disturbance V'pi was 1.77%, the population dynamic index Vpi and V'pi were both greater than 0, and the probability of the population assuming risk under external disturbance was Pmax 6.25%. The above results indicated that the P. yunnanensis population is a growing population structure with some resistance to disturbance. Furthermore, the P. yunnanensis population had a survival curve tending to the type of Deevey-II, and the survival analysis found that the survival rate, cumulative mortality rate, mortality density and hazard rate varied greatly from Ⅰ to Ⅶ age classes (diameter at breast height<35 cm), and stabilized from Ⅶ to XVI age classes (diameter at breast height 35-80 cm). The spectral analysis exhibited that the population dynamics of P. yunnanensis followed one major trend, and the Ⅲ age class (diameter at breast height 10-15 cm) was the main stage affecting the population size. The above results reveal that the number of individuals in the lower age classes of P. yunnanensis populations in the Yunlong Tianchi Nature Reserve fluctuates greatly, with more individuals dying and the upper age classes declining. It is suggested that the young and middle-aged natural P. yunnanensis forests in the Yunlong Tianchi Nature Reserve can be nurtured and intercut to promote their population growth, development and renewal. Based on all these results, the population of P. yunnanensis was found to remain sustainable in the long term, although it fluctuates in the middle and lower ages. 参考文献 相似文献 引证文献

Gender differences in fresh vegetable intake from 1979 to 2017 in Finland

PurposePrevious research has shown that in contemporary societies, women have a healthier dietary intake than men. However, no research has examined how this gender gap develops over the long term. The present study examined how gender differences in fresh vegetable intake frequency have evolved from 1979 to 2017 in Finland and whether differences are affected by age or educational level.Design/methodology/approachThe data were derived from annually repeated, nationally representative “Health Behaviour and Health among the Finnish Adult Population” and “Regional Health and Well-being (RHW)” surveys on the health habits of the Finnish population. The dataset is a time series of repeated cross-sectional surveys. In total, the data sample comprised 161,996 Finns aged 20–64 years. Descriptive methods and logistic regression were used for the analysis.FindingsDuring 1979–2017, the prevalence of daily vegetable intake increased from 12 to 35% among men and from 18 to 56% among women. Thus, the magnitude of the gap between genders doubled across the study period. The increased vegetable intake was partly explained by the changing education and age structures of society. Potential explanations and avenues for future research are also discussed. Policy implications depend on whether the findings are interpreted as a case of health differences or health inequality.Originality/valueThis study used a long time series to analyse how gender differences in vegetable intake have evolved in a Nordic welfare state context. It showed that the gap in fresh vegetable intake between men and women has widened.

Impact of Population Age Structure on Food Consumption Structure of Residents in Beijing

Based on the Beijing panel data from 1990 to 2019, this paper expands the traditional Almost Ideal Demand System (AIDS) model by introducing the nutritional needs indicators by age structure and quantitatively analyzes the structure and characteristics of household food consumption in Beijing. The study estimates and compares the income elasticity, price elasticity, nutritional demand elasticity of food consumption structure, and the per capita food consumption in Beijing is predicted. The results show that commodity prices and income are still the key factors affecting consumer demand. The change in the population's age structure also has a corresponding impact on the consumption structure. The consumption structure of Beijing is in the stage of optimization, and relevant departments should formulate relevant policies to increase farmers' income and stabilize prices.

Trends of Total Knee Arthroplasty According to Age Structural Changes in Korea from 2011 to 2018.

Total Knee Arthroplasty (TKA) is one of the most commonly performed surgeries worldwide since it can improve pain, quality of life, and functional outcome. Due to the expansion of hospitals specialized in joint surgery, the topography of TKA implementation in Korea is changing. This study analyzed longitudinal trends of TKA based on changes in age distribution, sex, hospital, and region based on the Health Insurance Review and Assessment Service (HIRA) of Korea database. Data were collected from the National Health Insurance Service (NHIS), the Korean Statistical Information Service (KOSIS), and the Health Insurance Review and Assessment Service (HIRA) in Korea for the period 2011–2018. Results show the total number of surgeries increased and the number of patients by age decreased in those under the age of 70, while the number of patients over 70 years of age increased. A remarkable increase in women was found, and there was no significant difference between regions. TKA is spreading in a more universal and easily accessible form in Korea and has increased more in other relatively small medical institutions compared to tertiary referral medical centers. Due to the increase of orthopedics’ specialized hospitals and clinics, TKA is becoming more prominent in those hospitals.

Impact of the War in Croatia (1991-1995) on the Differentiation of Age Structure between Serbs and Croats: A Case Study of the Banija Region

AbstractAging is the subject of various studies by the scientific community and monitoring by responsible institutions. The intensity of aging and the proportion of age groups among various communities differ due to different socio-economic conditions and characteristics. This article researches the impact of the war in Croatia 1991–1995 and postwar living conditions on the divergence of population aging in the ethnically heterogeneous Banija region. The first postwar census in 2001 recorded a population decline of 44.9% compared to the 1991 census. We analyze the effects of the war on changes in ethnic and age structure, as well as their interrelations. The quantitative and qualitative magnitude of these demographic changes in the inter-census period had a decisive influence on the correlation of age and ethnic structure. The article examines whether the relative share of Serbs or Croats in the total population of a settlement affects the average age of the settlement. The results confirmed that the Serbs are older than the Croats, and are in the phase of the most advanced demographic age. These changes raise the question of the demographic future and the biological viability of the Serbs, who were the majority in the region before the war.

Trends in short sleep duration in the National Health and Interview Survey 2004-2018: A Decomposition Analysis

Abstract Since the early 2000s, it is increasingly common that people have short sleep durations (&amp;lt;=6 per 24-hour), making this a high-prevalence public health issue, especially among Black individuals. We investigate how trends in short sleep duration are influenced by changes in population aging, socioeconomic factors (e.g., education, labor force participation, marital status), and health conditions and behaviors (e.g., pain, smoking, drinking, obesity, psychological distress). We use the pooled cross-sectional data from the 2004-2018 National Health and Interview Survey, a large and nationally representative study. We partition overall trends in short sleep duration into (a) compositional effects due to distributional changes in age structure, socioeconomic and health factors and (b) unexplained rate effects. Subsequently, we compare the relative contribution of each factor to the total compositional effects among Black and White participants. Results demonstrate that greater education is associated with greater prevalence of short sleep duration among Black Americans, but reduced prevalence among White Americans. For both racial groups, population aging contributes relatively little to temporal patterns in short sleep duration; by contrast, higher distress and lower labor force participation in recent years are associated with the increasing prevalence of short sleep duration.

The Human Tide: A Review Essay

The Human Tide: How Population Shaped the Modern World, by Paul Morland, argues for the importance of demography in both historical events and our current situation. Intended for a general audience, the book traces demographic developments from the late eighteenth century, arguing that the timing and pace of demographic change helps to explain why some countries became powerful and others did not. The author continues the story into the twentieth century, discussing the changes in age structure and internal ethno-religious balances that are consequences of demographic patterns. Many readers will find the questions and themes in The Human Tide interesting. Unfortunately, the book misrepresents some research findings and is confused about important demographic concepts. The Human Tide deals with fundamental changes in human society over the past two centuries, but for a clear account of those changes, readers will have to go elsewhere. (JEL I12, J11, J13, J15, K37, N30)

Organising a juvenile ratio monitoring programme for 10 key waterbird species in the Yangtze River floodplain: analysis and proposals

BackgroundIn the face of continued degradation and loss of wetlands in the Yangtze River floodplain (YRF), there is an urgent need to monitor the abundance and distribution of wintering waterbirds. To understand fully observed annual changes, we need to monitor demographic rates to understand factors affecting global population size. Annual reproduction success contributes to dynamic changes in population size and age structure, so an assessment of the juvenile ratio (i.e. first winter birds as a proportion of total number aged) of overwintering waterbirds can be an important indicator of the reproductive success in the preceding breeding season.MethodsDuring 2016–2019, we sampled juvenile ratios among 10 key waterbird species from the wetlands in the YRF. Based on these data, we here attempt to establish a simple, efficient, focused and reliable juvenile ratio monitoring scheme, to assess consistently and accurately relative annual breeding success and its contribution to the age structure among these waterbird species.ResultsWe compared juvenile ratio data collected throughout the winter and found that the optimal time for undertaking these samples was in the early stages of arrival for migratory waterbirds reaching their wintering area (early to mid-December). We recommend counting consistently at key points (i.e. those where > 1% biogeographical flyway population were counted) at sites of major flyway importance (Poyang Lake, East Dongting Lake, Shengjin Lake, Caizi Lake, Longgan Lake and Chen Lake). Based on this, the error rate of the programme (155 planned points, the count of 10 waterbird species is 826–8955) is less than 5%.ConclusionsWe established a juvenile ratio monitoring programme for 10 key waterbird species in the wetlands of the YRF, and discuss the feasibility and necessity of implementing such a future programme, and how to use these data in our monitoring and understanding of the population dynamics of these waterbird populations.

The Estimation of the Potential Human Capital Accumulation Rate of China in the Future

From the perspective that the change in population age structure could affect human capital accumulation, this paper introduces a concept of “the potential growth speed in human capital stock” and discusses the future of China’s human capital growth from different aspects. This paper uses the perpetual inventory method and China’s sixth national population census data to predict the maximum potential space for China’s human capital stock growth in the future. Firstly, we use the average years of schooling of the working-age population as an index to measure the human capital stock. Though decomposing the differences in human capital stock, we introduce the concept of potential growth speed in human capital stock. Secondly, by decomposing accumulation rate of human capital stock in China, differences of human capital stock between China and South Korea, and differences of human capital stock between China and Japan, this paper finds that the age structure change will have a negative factor on China’s accumulation of human capital in the next 20 years. To conclude, China will probably accumulate human capital at a much faster rate until 2040, but the human capital growth potential is fully exploited on the condition of that.

Trends of Colorectal Cancer Incidence in Kazakhstan.

Background and objective:Colorectal cancer (CRC) remains one of the most widespread human malignancies. The aim of this study was to study trends of the incidence of CRC in Kazakhstan. Materials and Method:This retrospective study was done using descriptive and analytical methods of oncoepidemiology. Results:During the study period from 2009 to 2018, 28,950 new cases of CRC were recorded, 13,779 (47.6%) cases were allocated to men and 15,171 (52.4%) to women. It was found that the incidence rate of CRC increased from 14.79 (2009) to 17.72 in 2018 and the overall growth was 2.93 cases per 100,000. This increase was due to the age structure – ∑ΔA=+1.42, the risk of acquiring illness – ∑ΔR=+1.31, and their combined effect – ∑ΔRA=+0.20. The component analysis results revealed that the increase in the number of patients with CRC was mainly due to the growth of the population (ΔP=+37.7%), changes in age structure (ΔA=+26.6%), and changes associated with the risk of acquiring illness (ΔR=+24.6%). The number of patients (both sexes) was increasing in many regions largely due to the influence of the age structure of the population. In addition, it was found that growth in the number of patients in most regions, both men and women, was associated primarily with the risk of acquiring illness. Conclusion:The findings of the current study showed increasing trends in the incidence of CRC in all regions of the country. These changes were mainly influenced by demographic factors (population size and age structure), risk of acquiring the disease, and their combined effect.

China's low fertility may not hinder future prosperity

China's low fertility is often presented as a major factor which will hinder its prosperity in the medium to long term. This is based on the assumed negative consequences of an increasing old-age dependency ratio: a simplistic measure of relative changing age structures. Based on this view, policies to increase fertility are being proposed after decades of birth restriction policies. Here, we argue that a purely age structure-based reasoning which disregards labor force participation and education attainment may be highly misleading. While fertility has indeed fallen to low levels, human capital accumulation has been very strong-especially among younger cohorts. Factoring in the effects of labor force participation and educational attainment on productivity, a measure called "productivity-weighted labor force dependency ratio" can more accurately capture the economic implications of demographic change. When using this ratio, a much more optimistic picture of the economic (and social) future of China can be envisaged.

Population age structure of ostracods in lake sediment and its implication for within-lake transport of microfossils

In palaeolimnology, microfossils play an important role as ecological indicators of lake history. A reliable interpretation of microfossil data requires a comprehensive understanding of transport processes as well as determining whether microfossil assemblages are representative of their living communities. The occurrence of transport in ostracod taphocoenoses can be identified from the population age structure of valves. In this study, 23 surface sediment samples from Dalongchi Lake, northwestern China, were analysed for species composition, and 16 were also analysed for the population age structure of Fabaeformiscandona gyirongensis. Ostracod valves are dominated by F. gyirongensis, with frequently occurring Ilyocypris sp. in the surface sediments. The distribution and abundance of ostracods are significantly correlated with the sampling depth and grain size, implying that hydrological conditions are the major controlling factor. The dominant species F. gyirongensis seems to prefer relatively deep and stable lacustrine conditions, while Ilyocypris sp. seems to prefer shallow conditions with rich submerged macrophytes and relatively coarse substrate in Dalongchi Lake. The spatial changes in the population age structure of F. gyirongensis match the different hydrodynamic regimes within the lake, with abundant early and middle instars in deeper waters and abundant middle and late instars in shallower waters, denoting that downslope transport of valves may be responsible for the spatial changes in the population structure. Our findings, together with previous works, indicate that downslope transport of instars and subsequent depth differentiation of the population structure of ostracods can occur for different species in both marine and lacustrine settings, which potentially leads to some biases based on the “in situ” inference of microfossils in palaeoenvironmental reconstruction. Hence, careful transport process assessment of fossil assemblages based on population age structure and other characteristics, such as the ratios of adults to juveniles and carapaces to valves, is a valuable prerequisite for palaeoenvironmental analysis.