Using a theoretical model, this article concludes that age structures influence people＇s propensity to save and thereby influence their capital intensity. In the context that capital and labor are in a substitutional...Using a theoretical model, this article concludes that age structures influence people＇s propensity to save and thereby influence their capital intensity. In the context that capital and labor are in a substitutional relation, increased capital intensity may lead to a drop of labor income share. We perform empirical research with provincial-level data from 1990 to 2007 and have proved that the rising of the old dependency ratio and the decrease of the children dependency rate both contribute to the fall of labor income share. This assumption still holds true after the authors control the influences of other potential factors that may influence labor income share展开更多
For a long time, China has large population, so the labor-intensive products become the comparative advantage.This paper analyzes the influences of population age structure＇s changes on the export commodity structure...For a long time, China has large population, so the labor-intensive products become the comparative advantage.This paper analyzes the influences of population age structure＇s changes on the export commodity structure of our country and draws conclusions.展开更多
COVID-19 has triggered an unprecedented public health crisis and a global economic shock.As countries and cities have transitioned away from strict pandemic restrictions,the most effective reopening strategies may var...COVID-19 has triggered an unprecedented public health crisis and a global economic shock.As countries and cities have transitioned away from strict pandemic restrictions,the most effective reopening strategies may vary significantly based on their demographic characteristics and social contact patterns.In this study,we employed an extended agespecific compartment model that incorporates population mobility to investigate the interaction between population age structure and various containment interventions in New York,Los Angeles,Daegu,and Nairobi e four cities with distinct age distributions that served as local epicenters of the epidemic from January 2020 to March 2021.Our results demonstrated that individual social distancing or quarantine strategies alone cannot effectively curb the spread of infection over a one-year period.However,a combined strategy,including school closure,50%working from home,50%reduction in other mobility,10%quarantine rate,and city lockdown interventions,can effectively suppress the infection.Furthermore,our findings revealed that social-distancing policies exhibit strong age-specific effects,and age-targeted interventions can yield significant spillover benefits.Specifically,reducing contact rates among the population under 20 can prevent 14%,18%,56%,and 99%of infections across all age groups in New York,Los Angeles,Daegu,and Nairobi,respectively,surpassing the effectiveness of policies exclusively targeting adults over 60 years old.In particular,to protect the elderly,it is essential to reduce contacts between the younger population and people of all age groups,especially those over 60 years old.While an older population structure may escalate fatality risk,it might also decrease infection risk.Moreover,a higher basic reproduction number amplifies the impact of an older population structure on the fatality risk of the elderly.The considerable variations in susceptibility,severity,and mobility across age groups underscore the need for targeted interventions to effectively control the spread of COVID-19 and mitigate risks in future pandemics.展开更多
This paper was based on data collected during the 38th and 39th Chinese National Antarctic Research Expeditions in the Amundsen Sea. The spatiotemporal distribution patterns of length(total length, AT) and sexual matu...This paper was based on data collected during the 38th and 39th Chinese National Antarctic Research Expeditions in the Amundsen Sea. The spatiotemporal distribution patterns of length(total length, AT) and sexual maturity stages of Antarctic krill(Euphausia superba) were examined. The age structure and geographic distribution of cluster groups also were studied. The results reveal significant diurnal variations in the length and maturity stages of Antarctic krill during the morning(MRN) to morning twilight(MTW) period, with mean lengths ranging from 28.92 to 45.87 mm. Two cyclical patterns were observed.Regarding maturity stages, the krill were composed of juveniles, adult males, and adult females in increasing order of proportion,with a notably higher proportion of non-gravid females compared to gravid females, and mainly distributed in evening twilight(ETW) to dawn(DWN), MTW to day(DAY), MRN to MTW, MRN to MTW and night(NIT) to DAY periods, respectively.Significant spatial variations in krill length and maturity stages occur, with a marked regional boundary around 130°W. K-means clustering analysis of krill length identified Group Ⅰ, Group Ⅱ, and Group Ⅲ, with dominant age classes of 3+, 0 and 3+, and 3+to 4+, respectively. Group Ⅱ was widely distributed in the surveyed waters, whereas Group Ⅰ and Group Ⅲ were distributed only in waters west of 130°W. The study area features a significant continental slope, where adults and gravid females were primarily distributed on its slopes and to the south. This spatial pattern also profoundly influenced the distribution of different cluster groups.展开更多
A model which describes the dynamics of an SIS epidemic in an age-structured and time dependent population is considered. The global behavior of the model with a special form for the infective force is obtained. The e...A model which describes the dynamics of an SIS epidemic in an age-structured and time dependent population is considered. The global behavior of the model with a special form for the infective force is obtained. The existence and uniqueness of the solution and nontrivial endemic equilibrium state are proved.展开更多
The age structure of the Chinese population is entering a process of generalized aging in which the major age groupings will see a fall in the ratio of younger age groups and a rise in the ratio of older age groups,wi...The age structure of the Chinese population is entering a process of generalized aging in which the major age groupings will see a fall in the ratio of younger age groups and a rise in the ratio of older age groups,with varying levels of socioeconomic significance for the entire population system.The implementation of the unconditional two-child policy(quanmian erhai zhengce)has not changed this general trend.The early stage of population aging(2011-2060)is one of the high-speed development of generalized aging with multiple growth peaks and fluctuations in the size,growth rate and internal structure of the major age groupings.From the perspective of generalized population aging,China’s future contains four major systemic demographic dividends and faces four major systemic demographic risks.The early stage of aging is the most important period for the transformation of the population age structure.If society can adjust to the aging trend and the phased nature of the development of this trend,it will be able to seize the initiative in long-term development.展开更多
文摘Using a theoretical model, this article concludes that age structures influence people＇s propensity to save and thereby influence their capital intensity. In the context that capital and labor are in a substitutional relation, increased capital intensity may lead to a drop of labor income share. We perform empirical research with provincial-level data from 1990 to 2007 and have proved that the rising of the old dependency ratio and the decrease of the children dependency rate both contribute to the fall of labor income share. This assumption still holds true after the authors control the influences of other potential factors that may influence labor income share
文摘For a long time, China has large population, so the labor-intensive products become the comparative advantage.This paper analyzes the influences of population age structure＇s changes on the export commodity structure of our country and draws conclusions.
基金funding from the National Natural Science Foundation of China(grant 71904104)the China Postdoctoral Science Foundation(grant 2019M650726)+1 种基金funding from Qiushi Foundation,the Resnick Sustainability Institute at California Institute of Technology and the National Natural Science Foundation of China(grant 71874097 and 41921005)DMK gratefully acknowledges the support of the Zaffaroni Family Foundation,the Karsten Family Foundation,and US NSF CyberSEES Grant 1539585 and NSF InFEWS grant DGE 1633740.
文摘COVID-19 has triggered an unprecedented public health crisis and a global economic shock.As countries and cities have transitioned away from strict pandemic restrictions,the most effective reopening strategies may vary significantly based on their demographic characteristics and social contact patterns.In this study,we employed an extended agespecific compartment model that incorporates population mobility to investigate the interaction between population age structure and various containment interventions in New York,Los Angeles,Daegu,and Nairobi e four cities with distinct age distributions that served as local epicenters of the epidemic from January 2020 to March 2021.Our results demonstrated that individual social distancing or quarantine strategies alone cannot effectively curb the spread of infection over a one-year period.However,a combined strategy,including school closure,50%working from home,50%reduction in other mobility,10%quarantine rate,and city lockdown interventions,can effectively suppress the infection.Furthermore,our findings revealed that social-distancing policies exhibit strong age-specific effects,and age-targeted interventions can yield significant spillover benefits.Specifically,reducing contact rates among the population under 20 can prevent 14%,18%,56%,and 99%of infections across all age groups in New York,Los Angeles,Daegu,and Nairobi,respectively,surpassing the effectiveness of policies exclusively targeting adults over 60 years old.In particular,to protect the elderly,it is essential to reduce contacts between the younger population and people of all age groups,especially those over 60 years old.While an older population structure may escalate fatality risk,it might also decrease infection risk.Moreover,a higher basic reproduction number amplifies the impact of an older population structure on the fatality risk of the elderly.The considerable variations in susceptibility,severity,and mobility across age groups underscore the need for targeted interventions to effectively control the spread of COVID-19 and mitigate risks in future pandemics.
基金supported by the 38th and 39th CHINAREs and all members of the two Antarctic cruisessupported by Ministry of Natural Resources of the People’s Republic of China and the Chinese Arctic and Antarctic Administration。
文摘This paper was based on data collected during the 38th and 39th Chinese National Antarctic Research Expeditions in the Amundsen Sea. The spatiotemporal distribution patterns of length(total length, AT) and sexual maturity stages of Antarctic krill(Euphausia superba) were examined. The age structure and geographic distribution of cluster groups also were studied. The results reveal significant diurnal variations in the length and maturity stages of Antarctic krill during the morning(MRN) to morning twilight(MTW) period, with mean lengths ranging from 28.92 to 45.87 mm. Two cyclical patterns were observed.Regarding maturity stages, the krill were composed of juveniles, adult males, and adult females in increasing order of proportion,with a notably higher proportion of non-gravid females compared to gravid females, and mainly distributed in evening twilight(ETW) to dawn(DWN), MTW to day(DAY), MRN to MTW, MRN to MTW and night(NIT) to DAY periods, respectively.Significant spatial variations in krill length and maturity stages occur, with a marked regional boundary around 130°W. K-means clustering analysis of krill length identified Group Ⅰ, Group Ⅱ, and Group Ⅲ, with dominant age classes of 3+, 0 and 3+, and 3+to 4+, respectively. Group Ⅱ was widely distributed in the surveyed waters, whereas Group Ⅰ and Group Ⅲ were distributed only in waters west of 130°W. The study area features a significant continental slope, where adults and gravid females were primarily distributed on its slopes and to the south. This spatial pattern also profoundly influenced the distribution of different cluster groups.
基金This work is supported by the National Natural Sciences Foundation of China.
文摘A model which describes the dynamics of an SIS epidemic in an age-structured and time dependent population is considered. The global behavior of the model with a special form for the infective force is obtained. The existence and uniqueness of the solution and nontrivial endemic equilibrium state are proved.
文摘The age structure of the Chinese population is entering a process of generalized aging in which the major age groupings will see a fall in the ratio of younger age groups and a rise in the ratio of older age groups,with varying levels of socioeconomic significance for the entire population system.The implementation of the unconditional two-child policy(quanmian erhai zhengce)has not changed this general trend.The early stage of population aging(2011-2060)is one of the high-speed development of generalized aging with multiple growth peaks and fluctuations in the size,growth rate and internal structure of the major age groupings.From the perspective of generalized population aging,China’s future contains four major systemic demographic dividends and faces four major systemic demographic risks.The early stage of aging is the most important period for the transformation of the population age structure.If society can adjust to the aging trend and the phased nature of the development of this trend,it will be able to seize the initiative in long-term development.
