Effects Of Age Structure Research Articles

Patterns of parasite prevalence and individual infection in yellow‐bellied marmots

AbstractPatterns of infection and prevalence result from complex interactions between hosts and parasites, the effects of which are likely to vary by species. We investigated the effects of age, sex and season on the likelihood of individual infection, and the effects of host population size, sex ratio and age structure on parasite prevalence. We capitalized on data from a long‐term study of yellow‐bellied marmots Marmota flaviventris potentially infected with fecal–orally transmitted intestinal parasites (Ascaris sp., Eimeria spp. and Entamoeba sp.), ectoparasitic fleas Thrassis stanfordi, and a flea‐ and louse‐transmitted blood parasite Trypanosoma lewisi. Patterns of individual‐ and group‐level infection varied widely by parasite. Yearlings were more likely to be infected with Tr. lewisi and Ascaris. Yearlings were also slightly more likely than adults to have Eimeria, but female yearlings had higher infection levels than female adults, while male yearlings had lower infection levels than male adults. Entamoeba infection decreased as the season progressed. Adults and males were more likely to be infected with Th. stanfordi. Ascaris prevalence increased with colony size. There were no significant relationships between colony size and prevalence of Entamoeba, Tr. lewisi, Eimeria or Thrassis. There was a small, but significant positive correlation between male‐biased sex ratio and prevalence of fleas. The host population's age structure affected the prevalence of infection of Ascaris and Eimeria. Overall intestinal parasite diversity increased with colony size. Taken together, our results show a great deal of variation in the likelihood of individual infection and patterns of parasite prevalence in marmots.

Quantifying the Effect of Age Structure on Voter Registration

ObjectiveWhere population subgroups have distinctly “young” or “old” adult age distributions, their observed overall rates of political participation may differ for this demographic reason. Age standardization can quantify the proportion of an observed difference in registration rates attributable to age structural differences between two populations, thereby facilitating comparison of political participation across subgroups.MethodsI illustrate the derivation and interpretation of an age‐standardized registration rate. This rate weights a set of observed age‐specific registration rates with a standard age distribution to create a hypothetical total (all‐ages) registration rate, to afford an undistorted comparison of Hispanic and non‐Hispanic white voter registration.ResultsFor seven communities studied here, differences in adult age structure account for as much as one‐third of the observed difference in the voter registration rates of adult Hispanics and non‐Hispanic whites in a community. The effect of age structure is most apparent in those communities registering substantial influxes of young‐adult Hispanics.ConclusionAge standardization is a useful technique to control for differences in population structure that may obscure a comparison of political participation across subgroups.

Demographic Dividends Revisited

This paper revisits demographic dividend issues after almost 2 decades of debate. In 1998, David Bloom and I used a convergence model to estimate the impact of demographic-transition-driven age structure effects and calculated what the literature has come to call the “demographic dividend.” These early estimates seem to be similar to those coming from more recent overlapping generation models, when properly estimated. Research has shown that the demographic dividend is not simply a labor participation rate effect, but also a growth effect. Life-cycle savings, investment deepening, foreign capital flows, and schooling have all been greatly affected by the demographic transition. The paper discusses just how much of these positive growth effects are based on accelerating human capital accumulation induced by demand-side quality–quantity trade-offs versus a co-movement between demographic transitions and public schooling supply-side expansions. Since emigration has been driven in part by demography, it has wasted some of the demographic dividend by brain drain. In addition, within-country rural–urban migrations have also been driven in part by demographic transitions with different spatial timing. Finally, the paper shows how lifetime—not just annual—income inequality has been influenced by demographic transitions.

Factors in the Response of Agave Weevil,Scyphophorus acupunctatus(Coleoptera: Curculionidae), to the Major Compound in its Aggregation Pheromone

The agave weevil, Scyphophorus acupunctatus Gyllenhal (Coleoptera: Curculionidae), causes economic damage to Agave tequilana F.A.C Weber var. ‘Blue’, A. fourcroydes Lem., A. angustifolia Haw, and Polianthes tuberosa Lem. Currently, the synthetic compound 2-methyl-4-octanone is used to monitor S. acupunctatus, but factors involved in chemical communication by S. acupunctatus need to be better understood. We used electroantennography, olfactometer bioassays, and analysis of the COI mitochondrial region to study the effect of sex, age, and genetic structure on the electrophysiological response and search behavior by S. acupunctatus to 2-methyl-4-octanone. We showed that electrophysiological and behavioral response to 2-methyl-4-octanone differed among populations of agave weevils from different crops and geographical regions. Furthermore, it was determined that the age of the insect was involved in both responses. Also, genetic changes in mitochondrial DNA suggest groups that differ in their response of S. acupunctatus to 2-methyl-4-octanone. This information provides a baseline to design a method to control agave weevil based on geographical region and type of host.

Population growth across heterogeneous environments: effects of harvesting and age structure

Population growth is affected by several factors such as climate, species interaction and harvesting pressure. However, additional complexity can arise if fishing increases the sensi- tivity to environmental variability. To predict the effects of fisheries and climate on marine popu- lations, there is a need for improved understanding of how they affect key ecological processes such as population growth. In this study, we used a comparative approach investigating commer- cially fished species across different ecosystems: the Norwegian Sea−Barents Sea (Northeast Arc- tic cod), the North Sea (North Sea cod), the Atlantic Ocean (European hake), the Mediterranean Sea (European hake), and the Gulf of Alaska and Bering Sea (walleye pollock). Our objective was to compare the effects of commercial fisheries, age structure and environmental variability on population growth rate. We show that although all stocks experienced a decline in abundance, only 3 of them showed a concomitant decreasing trend in generation time (South Atlantic hake, North Atlantic hake and Northeast Arctic cod), suggesting a fishing-induced erosion in their age structure. Intra-specific analysis shows that changes in generation time triggered an increase in the relative contribution of recruitment to population growth. Furthermore, the contribution from recruitment to population growth changes due to large-scale climate indices or regional-scale environmental covariates, such as sea temperature. This study illustrates how and where the inter- action between large-scale ecological patterns and regional/short-scale processes are important for designing management regulations.

Articulation rate: Effects of age, fluency, and syntactic structure

We report basic findings on articulation rate effects derived from experimental research on children's sentence planning. The experiments were designed to evaluate production processes with attention to syntactic variables while controlling for lexical and phonological variables. Articulatory rate measures showed (1) rates differed for children (3–8.11) and adults, with adult rates significantly faster than child rates; (2) the effects of fluent and dysfluent host utterances on fluent substrings differed for adults and children; (3) rate patterns for relative clause and conjoined clause utterances differed, both from each other and across age group.

Maternal age, fecundity, egg quality, and recruitment: linking stock structure to recruitment using an age-structured Ricker model

Understanding the process of recruitment is fundamental to fisheries biology and management. However, recruitment in natural populations is highly variable and rarely well described by classical stock–recruitment relationships (SRRs). Recent analyses suggest that the age composition of the spawning biomass may play an important role in the mismatch between SRRs and data. Here we develop a generalization of the Ricker SRR that incorporates age structure by allowing mortality and fecundity rates to depend on maternal age. We provide a flexible SRR with biologically interpretable parameters that can be estimated from existing fisheries time series and use a Bayesian framework that enables parameters to be informed by experimental data. We apply our method to the Icelandic population of Atlantic cod ( Gadus morhua ) and show models that include age structure effects outperform the classical Ricker SRR that ignores age structure. Our results indicate a strong effect of spawning stock age structure on recruitment dynamics in this population. Our approach provides a biologically interpretable and immediately applicable method for investigating the consequences for spawning stock age structure on recruitment.

Impact of Demographic Structure on Carbon Di Oxide Emissions: India's Sectoral Experience

In the paper I analyze the effect of population age structure on India’s environment burden. I conduct the analysis for 19 consumption sectors using an extension of IPAT framework. Results show that the per capita environment burden peaks for the age cohort between forty-one and fifty and declines thereafter. Results also show that Education, Clothing and Cereals have the highest environment burden footprint among the sectors analyzed. Keeping everything else constant, future demographic changes should have a marginal effect on the environment burden of the sectors in question.

Mating Group Size and Stability in Reindeer Rangifer tarandus: The Effects of Male Characteristics, Sex Ratio and Male Age Structure

AbstractIn polygynous mating systems, males compete intensely for mates and may mate several females during a single reproductive season. Accordingly, factors influencing the ability of males to control a larger number of females during the breeding season can provide information on the processes underlying sexual selection. In ungulates, age, body mass and social rank are considered good predictors of the reproductive success of males, but how male age structure and sex ratio in the population influence mating group (MG) dynamics has received little empirical testing. Between 1996 and 2005, we manipulated male age‐ and sex structure and monitored MG dynamics in a reindeer (Rangifer tarandus) population. We investigated the influence of male characteristics, percentage of males and male age structure on MG size and stability. We found that males with higher social rank (that were also older and heavier) controlled larger MGs (therefore had greater mating opportunities) and had more stable MGs (corresponding to a higher ability to maintain and control females) than males of lower social rank. Moreover, MG size and MG stability decreased as the percentage of males in the population increased, most likely resulting from greater male–male competition and increased female movements. Male age structure did not influence MG stability. Given the positive relationship between mating success and MG size (and likely MG stability), frequent female movements and intense competition among males to control females seem to be the principal components of reindeer MGs dynamic.

Interleg Coordination in Quiet Standing: Influence of Age and Visual Environment on Noise and Stability

ABSTRACT The authors reexamined reported effects of age, illumination, and stationary visible structure on the net center of pressure (COP) derived from dual, side-by-side force plates (J. Kinsella-Shaw, S. Harrison, C. Colon-Semenza, & M. Turvey, 2006) from the perspective of axial postural control. They questioned how left and right COP x (t), COP y (t), and vertically oriented ground reactive force, GRF z (t), coordinated during quiet standing. The Cross- recurrence Quantification (CRQ) revealed that coordination was primarily between fluctuations of similar direction, with coordination of left and right COP y (t) (anteroposterior fluctuations) dominant. CRQ also revealed that (a) illumination and structure affected the interlimb dynamics of older (M age = 72.2 ± 4.90 years) participants more than their younger (M age = 22.8 ± 0.83 years) counterparts, and (b) older participants exhibited greater interlimb entrainment (dynamical stability) in the presence of greater interlimb noise.

Demography, credit and institutions: A global perspective

This paper examines the role of age structure and its interaction with various capital market imperfections in driving international capital flows in an empirical framework. Using panel data covering the period 1970 to 2000 for up to 115 countries, results indicate the existence of a differentiated effect in the relationship between age structure and international capital flows. Good institutions allow for a differentiated impact of age structure on saving and investment, opening the scope for an impact of age structure in driving international capital flows. In contrast, bad institutions result in no effect of age structure on international capital flows. Despite increased credit availability contributing to reduced aggregate saving, this will nevertheless magnify the role of the population age structure in driving international capital flows. Over the past three decades, age structure changes are estimated to have contributed to improve the current account position by five per cent of GDP in more advanced aging countries. However, around the year 2020, population age structure changes are projected to deteriorate the current account position in the latter countries which will experience a drop in saving. In other regions, the faster the current aging process, the sharper the projected improvement in the current account position. This improvement is projected to reverse itself, at a later stage in time in regions with a slower aging process. Also, our results suggest that in order to take advantage of their younger population in the form of increased foreign capital inflows, countries that are less advanced in the demographic transition would need to improve the quality of their institutional arrangements before the “window of opportunity” closes.

POPULATION AGE STRUCTURE, SAVING, CAPITAL FLOWS AND THE REAL EXCHANGE RATE: A SURVEY OF THE LITERATURE

Abstract This paper surveys the existing literature on the effects of population age structure on saving, capital flows and the real exchange rate. We build on previous surveys of age structure and saving behaviour by including extensive discussion of international linkages, specifically the impact on capital flows and real exchange rates. We also point to unresolved issues that need to be addressed given that population aging has serious policy implications in the developed economies these days.

Voter Turnout in Japan: An Aggregate-Level Analysis of the 2005 and 2009 General Elections

This study examines the effects of socio-demographic and political factors on district level turnout in the 2005 and 2009 Japanese general elections. Results show that marginality is a strong predictor of turnout, while the effects of age structure, joblessness, and primary sector employment vary across elections.

The Baby Boom as it Ages: How Has it Affected Patterns of Consumption and Savings in the United States

Using detailed estimates of personal consumption expenditures at the state level for 1900, 1929, 1970, 1977, and 1982 developed by Stanley Lebergott, this paper demonstrates that the passage of the Baby Boom from childhood through the teen years and into family formation would have caused marked swings in patterns of aggregate consumption and savings in the United States during the past 50 years. The effect of age structure on personal consumption expenditures is estimated using population by single year of age from 0 to 85, revealing the expected pattern of life cycle consumption and savings in the adult years. In addition, however, a strong age-related pattern of consumption expenditures for children is demonstrated, with a strong savings component. The pattern, which emerges for children in all periods, is strongly U-shaped, with the highest levels of expenditure in the earliest years and for teens, and a marked pattern of saving when children are aged about 5 through 12.

Demographic structure and economic growth: Evidence from China

This paper examines the economic implications of demographic change in the Chinese context. We extend the growth equation by incorporating age structure dynamics and apply it to China’s provincial-level data during the period 1989–2004. We find that changes in demographic structure, especially the contribution of fertility decline to lower youth dependency, have helped fuel China’s economic growth since 1989. The effect of demographic change on income growth operates mainly through its impact on steady state income levels and the effect of age structure is more pronounced in provinces that are more open to market forces. We also find a significant feedback effect of economic growth on demographic behaviors through the mechanisms of birth rates, marriage age and life expectancy.

The Spatial Variation of Extreme Tooth Breakage in an Herbivore and Potential Age Structure Effects

Teeth are essential in mammals for the capture, handling and processing of food and self-defense. The rate of deterioration may affect longevity and indicate certain environmental conditions. The goal of this study was to characterize tooth conditions of moose (Alces alces) from multiple regions and to make inferences of possible causes of variation. An assessment of > 5500 moose incisors, found that the frequency of breakage and rate of decline in incisor integrity, with age, was much higher in Cape Breton and Newfoundland (breakage from 6% to 47%) than in New Brunswick, Ontario, New Hampshire, Vermont, and Yukon (breakage from 1% to 6%). Incisai degradation, among jurisdictions, differed significantly though population age structures did not appear different. The two jurisdictions most affected by incisai deterioration, Cape Breton and Newfoundland, are inhabited by genetically distinct subspecies, at higher densities than other regions; therefore, breakage may be linked to local environmental conditions.

THE RELEVANCE OF GENE FLOW IN METAPOPULATION DYNAMICS OF AN OCEANIC ISLAND ENDEMIC, OLEA EUROPAEA SUBSP. GUANCHICA

Theoretical and empirical studies suggest that geographical isolation and extinction-recolonization dynamics are two factors causing strong genetic structure in metapopulations, but their consequences in species with high dispersal abilities have not been tested at large scales. Here, we investigated the effect of population age structure and isolation by distance in the patterns of genetic diversity in a wind-pollinated, zoochorous tree (Olea europaea subsp. guanchica) sporadically affected by volcanic events across the Canarian archipelago. Genetic variation was assessed at six nuclear microsatellites (nDNA) and six chloroplast fragments (cpDNA) in nine subpopulations sampled on four oceanic islands. Subpopulations occurring on more recent substrates were more differentiated than those on older substrates, but within-subpopulation genetic diversity was not significantly different between age groups for any type of marker. Isolation-by-distance differentiation was observed for nDNA but not for cpDNA, in agreement with other metapopulation studies. Contrary to the general trend for island systems, between-island differentiation was extremely low, and lower than differentiation between subpopulations on the same island. The pollen-to-seed ratio was close to one, two orders of magnitude lower than the average estimated for other wind-pollinated, animal-dispersed plants. Our results showed that population turnover and geographical isolation increased genetic differentiation relative to an island model at equilibrium, but overall genetic structure was unexpectedly weak for a species distributed among islands. This empirical study shows that extensive gene flow, particularly mediated by seeds, can ameliorate population subdivision resulting from extinction-recolonization dynamics and isolation by distance.

The Impact of Realistic Age Structure in Simple Models of Tuberculosis Transmission

BackgroundMathematical models of tuberculosis (TB) transmission have been used to characterize disease dynamics, investigate the potential effects of public health interventions, and prioritize control measures. While previous work has addressed the mathematical description of TB natural history, the impact of demography on the behaviour of TB models has not been assessed.MethodsA simple model of TB transmission, with alternative assumptions about survivorship, is used to explore the effect of age structure on the prevalence of infection, disease, basic reproductive ratio and the projected impact of control interventions. We focus our analytic arguments on the differences between constant and exponentially distributed lifespans and use an individual-based model to investigate the range of behaviour arising from realistic distributions of survivorship.ResultsThe choice of age structure and natural (non-disease related) mortality strongly affects steady-state dynamics, parameter estimation and predictions about the effectiveness of control interventions. Since most individuals infected with TB develop an asymptomatic latent infection and never progress to active disease, we find that assuming a constant mortality rate results in a larger reproductive ratio and an overestimation of the effort required for disease control in comparison to using more realistic age-specific mortality rates.ConclusionsDemographic modelling assumptions should be considered in the interpretation of models of chronic infectious diseases such as TB. For simple models, we find that assuming constant lifetimes, rather than exponential lifetimes, produces dynamics more representative of models with realistic age structure.

Canadian Provincial Population Growth: Fertility, Migration, and Age Structure Effects

The effect of changes in rates of mortality, fertility, and migration depend not only on the age-specific patterns and levels of these rates, but on the age structure of the population. In order to remove the influences of the age structure and concentrate on the impact of the demographic rates themselves, a common practice is to analyze the influences of the rates for a standard age structure. This paper adapts the general approach of using a standard age structure to a stationary population equivalent (SPE) model, and analyzes current population change, using the SPE model, for provinces of Canada. Below-replacement fertility levels are only partially offset by net immigration. The SPE model evidences the decrease in the eventual provincial populations brought about by the below replacement fertility. Out-migration for some provinces to other areas of Canada accentuates their eventual population decreases.

¿De qué se mueren los ancianos en España?

Following the analyses of the standardized mortality rates, that allows to eliminate the effect of age structure, the impact of mortality is directly appreciated and the evolution of the main causes of death in the 80+ population in Spain between 1975 and 2007, is described. Using the Short-List of Eurostat, causes of death have been divided into 17 broad groups. The article analyzes the decline of mortality caused by the fall of circulatory diseases, mainly the cerebrovascular ones, and to a lesser extent, the respiratory diseases, ill-defined diseases and external causes. Inversely, in the remaining thirteen groups the mortality has increased over such period particularly, the neoplasms, nervous system diseases and mental disorders. Important differences by gender have been found, being neoplasms and respiratory diseases much higher in men, which would explain the greater men oldest-old mortality in Spain.