Simultaneous estimation of mortality and dispersal rates of an artificially released population

Mark-recapture methods cannot estimate both mortality and dispersal rates of a wild population simultaneously. However, when an artificially cultured population is released into an area, the initial population size and the initial population distribution are usually known. If artificially cultured individuals are released with marks or distinguished from wild individuals or if no wild individual exists in the study area, we can estimate both the mortality and dispersal rates of the artificial population. The numbers of dispersed and dead individuals are estimated from the dispersal rate from the diffusion model and the total decreasing rate estimated from a mark-recapture data. We can estimate both the time-dependent and time-independent dispersal rates from the data. We choose the best fit model that has the smallest value of Akaike's Information Criteria. We also consider ‘concentric circles approximation” of spatial distribution, in which the cumulative and frequency distributions are analytically obtained.     

A population density grid of the European Union

This paper describes four methods used to produce dasymetric population density grids combining population data per commune with CORINE Land Cover, a map available for all countries of the European Union. An accuracy assessment has been carried out for five countries for which a very reliable 1-km population density grid exists; the improvement, compared with the choropleth map per commune, ranges between 20% for the weakest result in Finland and 62% for the best result in the Netherlands. The best results are obtained with a method using logit regression to integrate information from the point survey LUCAS (Land Use/Cover Area frame Survey); however, performance differences between methods are moderate. The dasymetric grid is distributed free of charge by the European Environment Agency, for non-commercial use.     

Studies on the spatial distribution pattern of larvae of the mosquito,Anopheles sinensis, in rice fields

Summary The spatial distribution patterns of the population ofAnopheles sinensis larvae were studied in the rice field area in the suburb of Urawa city in Japan, during the summer seasons in 1973 and 1974. The distribution pattern of the larval population within the field, analysed by the m−m regression method, indicated that the basic component of larval distribution was not a group of individuals but a single individual and such components were distributed contagiously over the field. This basic pattern did not change significantly according to developmental stage, census date or field. Therefore, we could describe the distribution pattern of the population in a rice field by the single linear regression, x=0.021+1.339x(r²−0.912). Also, the relation for the whole population in the field area including the five fields could be shown by the linear regression, x=0.049+1.749x(r²−0.959). The value of α remained to be nearly equal to zero, but the value of β became larger than the value for the single-field relation. Such a change in distribution pattern seemed to reflect the greater heterogeneity in conditions among the fields than within individual field. Using the information on the distribution patterns mentioned above, some considerations were given on the sampling plans for mosquito larvae, including samplesize determination and application of sequential methods to estimate population size as well as to classify population level.     

Age structure,growth, attrition and accession: A new synthesis

This paper shows that each equation describing relationships among demographic parameters in a stable population is a special case of a similar and equally simple equation that applies to any closed population and demonstrates some implications of these new equations for demographic theory and practice. Much of formal demography deals with functions that pertain to individuals passing through life, or to a stationary population in which births of individuals are evenly distributed over time. These functions include life expectancy, probabilities of survival, net and gross reproduction rates, expected years spent in various states and the probability that certain events will occur in the course of life. The stable population model permits the translation of population structure or processes in a more general type of population, with constant growth rates, back into equivalent populations for a stationary population. The method for translation developed in this paper, requiring only a set of age-specific growth rates is even more general, applying to any population. Age specific growth rates may also be useful for performing reverse translations, between a population's life table and its birth rate or its age distribution. Tables of numbers of females by single years of age in Sweden are used to illustrate applications. Tables summarize the basic relations among certain functions in a stationary population, a stable population and any population. Applications of new equations, particularly to demographic estimation of mortality, fertility and migration, from incomplete data, are described. Some other applications include; the 2 sex problem, increment decrement tables, convergence of population to its stable form, and cyclical changes in vital rates. Stable population models will continue to demonstrate long term implications of changes in mortality and fertility. However, in demographic estimation and measurement, new procedures will support most of those based on stable assumptions.     

The Effect of Social Capital on Health Among European Older Adults: An Instrumental Variable Approach

One of the key policy question for an ageing population is the identifications of the factors which influence health. Very recently, an increasing interest on social capital has developed and, surprisingly, not much is known for the European population. This study analyzes the effect of structural social capital on health (measured as self-perceived health) of the individuals aged 60 or more residing in European countries. The sample comes from the fourth wave of the survey on health and retirement in Europe. We use an instrumental variables approach in order to account for the reverse causality between social capital and health. We found that structural social capital exerts a positive effect preventing people to suffer of a poor self-perceived effect. Results are robust to different estimation methods.     

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.     

Estimation of population size and survival of sheep blowfly,Lucilia cuprina, in the field from serial recoveries of marked flies affected by weather dispersal and age-dependent trappability

Summary A model is presented for analysis of mark-recapture data of mobile insects which, unlike the Lincoln Index, does not require marked individuals to remain within the sampling area or to mix uniformly with the wild population. The model assumes a single or multiple releases of marked insects from the centre of the sampling area and that captured individuals are not returned to the population. Dispersal rates of marked insects are estimable from serial recaptures and, for catches that are either unaffected by or have been corrected for weather effects, the model also provides estimates of mortality and age-dependent trappability. Application of the model is illustrated using mark-recapture data for adults of the Australian sheep blowflyLucilia cuprina. A Biometrics Unit report detailing all source data, program code and comparisons between dispersal models is available on request from the authors.     

Estimation of european corn borer egg masses density by sampling of runs

Summary Spatial distributions of individuals may be considered in two ways: Firstly, individuals are situated on a continuum. Secondly, individuals are situated on discrete units, for example, insect eggs on plants. The aim of this paper is to show that sometimes, in the latter case, sampling methods based on infestation runs can be of interest in estimating population density. Analytical results are obtained under complete spatial randomness hypothesis and alternative hypotheses. Sampling procedures with limited cost are discussed and the European corn borer (ECB) case is mainly considered.     

A simple method to estimate insect mortality from field census data: A modification of the Kiritani-Nakasuji-Manly method

Various methods have been proposed to estimate demographic parameters such as mortality from field census data. Simple methods proposed earlier are applicable only for limited situations. For example, the Kiritani-Nakasuji-Manly method is applicable only if individuals are observable until their death. Improved methods proposed later are not subject to such limitations, but are not so widely used in the field of applied entomology, probably because of the complexity of the calculations involved. In this paper, I propose an intermediate method that requires only a pocket calculator, considering the practical convenience for field scientists. This method, which is a modification of the Kiritani-Nakasuji-Manly method, gives an estimate of the number of individuals entering a stage from the frequency of two stages when the stage duration is known.     

Loss of genetic variability in a fragmented continuously distributed population

An individual-based simulation model was used to examine the effect of population subdivision, dispersal distance of offspring, and migration rates between subpopulations on genetic variability(H ₁ H _S andH _T ) in a continuously distributed population. Some difficulties with mathematical models of a continuously distributed population have been pointed out. The individual-based model can avoid these difficulties and can be used to examine genetic variability in a population within which individuals are distributed continuously and in which the dispersal of individuals is disturbed by geographical or artificial barriers. The present simulation showed that the pattern of decrease inH ₁ had three stages. During the first stage,H ₁ decreased at the rates predicted by Wright’s neighborhood size. During the second stage,H ₁ decreased more rapidly when the migration rate decreased, while during the third stage, it decreased less rapidly when the migration rate decreased. Increasing the number of subdivisions increased the rate of decrease after the 200th generation. The pattern of decrease inH _T was classified into 2 stages. During the first stage, the rates of decrease corresponded with those of a randomly mating population. During the second stage, a decrease in the migration rates of the subpopulations slowed the rate of decrease inH _T . A uniform spatial distribution and a reduced total dispersal distance of offspring causedH ₁ H _S , andH _T to decrease more rapidly. Habitat fragmentation in a continuously distributed population usually was detrimental to the genetic variability in the early generations. Other implications of the results for conservation are discussed.     

AN INVESTIGATION OF GENERALIZED RAKINGIN THE SYNTHETIC ESTIMATION OFPOPULATION SIZE

The problem of counting a population that is cross-classified with respect to demographic and geographic attributes is considered. A census is conducted in which individuals are “captured” with probabilities that are believed to be relatively constant within demographic categories. The census is followed by a random sample in which individuals are “recaptured” independently of the census. Using the two counts, capture-recapture estimates of the demographic category populations are obtained. A synthetic estimate of population size for a geographic entity is obtained by summing the corresponding adjustment factors (capture-recapture estimates divided by census counts) across all individuals captured by the census in the entity. The use of generalized raking is considered as a method for smoothing adjustment factors. It is found that generalized raking differs little from a class of weighted least squares regression models. This suggests that generalized raking does not offer an improvement over regression for smoothing adjustment factors. The efficiency loss of generalized raking relative to the best regression-based procedures can be substantial.     

Correcting missing-data bias in historical demography

Studies on population history are often based on incomplete records of life histories. For instance, in studies using data obtained from family reconstitution, the date of death is right censored (by migration) and the censoring time is never observed. Several methods for the correction of mortality estimates are proposed in the literature, most of which first estimate the number of individuals at risk and then use standard techniques to estimate mortality. Other methods are based on statistical models. In this paper all methods are reviewed, and their merits are compared by applying them to simulated and to seventeenth-century data from the English parish of Reigate. An ad hoc method proposed by Ruggles performs reasonably well. Methods based on statistical models, provided they are sufficiently realistic, give comparable accuracy and allow the estimation of several other quantities of interest, such as the distribution of migration times.     

Adult Mortality Five Years after a Natural Disaster

Exposure to extreme events has been hypothesized to affect subsequent mortality because of mortality selection and scarring effects of the event itself. We examine survival at and in the five years after the 2004 Indian Ocean earthquake and tsunami for a population‐representative sample of residents of Aceh, Indonesia who were differentially exposed to the disaster. For this population, the dynamics of selection and scarring are a complex function of the degree of tsunami impact in the community, the nature of individual exposures, age at exposure, and gender. Among individuals from tsunami‐affected communities we find evidence for positive mortality selection among older individuals, with stronger effects for males than for females, and that this selection dominates any scarring impact of stressful exposures that elevate mortality. Among individuals from other communities, where mortality selection does not play a role, there is evidence of scarring with property loss associated with elevated mortality risks in the five years after the disaster among adults age 50 or older at the time of the disaster.     

ENDOGENOUS NETWORKS IN RANDOM POPULATION GAMES

Population learning in dynamic economies traditionally has been studied in contexts where payoff landscapes are smooth. Here, dynamic population games take place over “rugged” landscapes, where agents are uncertain about payoffs from bilateral interactions. Notably, individual payoffs from playing a binary action against everyone else are uniformly distributed over [0, 1]. This random population game leads the population to adapt over time, with agents updating both actions and partners. Agents evaluate payoffs associated to networks thanks to simple statistics of the distributions of payoffs associated to all combinations of actions performed by agents out of the interaction set. Simulations show that: (1) allowing for endogenous networks implies higher average payoff compared to static networks; (2) the statistics used to evaluate payoffs affect convergence to steady-state; and (3) for statistics MIN or MAX, the likelihood of efficient population learning strongly depends on whether agents are change-averse or not in discriminating between options delivering the same expected payoff.     

Regulation of reproduction rate in a cyclic population of the red-backed vole,Clethrionomys rufocanus bedfordiae

Summary Changes of the components of reproduction were analyzed quantitatively in a two-year cyclic population (which has two peaks in alternate years during a five-year census) of the red-backed vole,Clethrionomys rufocanus bedfordiae, with reference to its regulatory mechanism: (1) Variation in sex ratios was not associated with population phase or density, although a higher percentage of females in mature individuals was observed in the increase phase. (2) Females attained to sexual maturity at younger age and at lighter body weight than did males. All the youngest mature individuals were found in the low and the increase phases. Age and size at maturity became older and larger as the population went toward the peak phase. (3) Maturation rate was strongly associated with population phase and density; this component is an important and good parameter to predict population trend. Maturation rates were in the order, the low phase>the increase phase>the peak phase>the decline phase; the differences in the rates among these phases were significant. Maturation rate was somewhat depressed when the population density exceeded about 40 individuals/ha. Changes in age at maturity and in maturation rate are interpreted as derivative phenomena related to the population density and the capacity of the number of mature voles per unit area. (4) The maximum number of mature individuals were 26 males/ha and 29 females/ha; there was almost no increase of the number of mature voles at higher population densities over about 40 individuals/ha. The number of exclusive home ranges per hectare calculated from the observed range lengths did not differ much from the maximum number of mature voles of either sex. (5) Length of breeding period was shorter in the high-density years than in the low-density years; the breeding started earlier and ended earlier in the former than that in the latter. In the increase phase a few voles reproduced in winter. (6) The percentage of pregnant females was significantly lower in the peak phase than those in the other phases.     

Subjective Quality of Life Among Individuals who are Homeless: A Review of Current Knowledge

The purpose of this article was to review the current literature on subjective quality of life (SQOL) in individuals who are homeless, with a focus on differences in SQOL (a) between homeless individuals and the general population, (b) based on housing situation, and (c) associated with demographic characteristics (such as age and gender), physical and mental health, and external variables such as service program type. A literature search was conducted of the online databases PubMed and PsycInfo for relevant studies published from January 1981 to August 2011. Although this review showed that individuals who are homeless tended to have lower levels of SQOL compared to the general population or housed individuals, it was also evident that our current understanding of the relationships between SQOL and various demographic, health, and other variables is based on very limited information. More information about the relationships between various characteristics and experiences of individuals who are homeless and SQOL is clearly needed to aid researchers, service providers, and policy-makers in addressing the needs of this population and examining the effectiveness of interventions to end homelessness and improve health among homeless individuals.     

A simplified robust estimate of the birth rate

It is shown that other estimates of the birthrate can be derived from Coale's robust birthrate estimate. Coale's estimate is nearly equal to the birthrate obtainable from reverse survival or reverse projection of the proportion of a population under age 15 (both sexes), or C(15), using a life table corresponding to l5. As a sequel to this, a birth rate estimate was obtained that does not require reference to stable population models and results in computational economy and ease. Taking advantage of the strong linear relation between l5 and 15L0, a simple robust estimate was derived of the birthrate that does not depend upon model stable populations or model life tables. After presenting these methods, their use is illustrated with data from several Asian and African countries. Coale (1981) suggested using the observed C(15) for both sexes and l5 to locate an appropriate stable population from a family of stable models to represent the observed population and to use its birthrate as an estimate of the population under study. The estimate of l5 can be obtained by any of the indirect methods like the Brass method. Coale observed that such methods yield birthrates that are not much affected even when the populations are not stable. He also suggested an adjustment for the stable birthrate for nonstability. To obtain the birthrate, one needs the denominator, namely, the number of persons that lived. This is obtained by using the rate of increase, r, which differs for a stable and a nonstable or observed population. Various methods can be used to obtain the time reference of the mortality estimate, l5, by providing years prior to the survey or census to which the l5 estimate is applicable.     

The Sustainability of Population Health

The study of population health encompasses analysis of the fundamental influences on human health, the consequences of such influences for societies and individuals, and the ways in which people and institutions respond to these consequences. A theme lacking from the present discourse is that of the sustainability of population health. To be sustainable, societies must respect the boundaries of natural systems and scorn disparities in standards of living. Preliminary analysis of data from 152 countries reveals an inverse relation between measures of population health and sustainability, although there are examples of societies where this inverse relation does not hold. Future research in population health should begin to question the sustainability of improving the health of some populations at the expense of others, and investigate how some societies appear to be able to achieve population health without compromising the health of the biosphere.     

The Biodemography of Variation in Human Frailty

A population is composed of individuals who are heterogeneous in their susceptibility to death and disease. This heterogeneity is reflected in the age-specific incidence or mortality (hazard) function. This variation has typically been hidden--that is, not measured directly--and has generally been modeled in a purely empirical statistical way, because there is no theory in demography for the distribution of frailty. A substantial fraction of variation in frailty, however, has an underlying genetic basis, for which there is a formal theory. This theory, based on evolutionary biology and on the nature of mendelian transmission, provides prior constraints on the distribution of variation in the population as well as providing methods for identifying genes involved in many important diseases. The accumulating effects of environmental exposures with age are another major component of variation in frailty. In some important instances, this variation and its effect on the age-specific hazard function can also be understood in terms of cause-specific biological processes. These biological considerations may enable demographers to model frailty, and thus mortality, in a better way.     

Day-of-the-Week Effects in Subjective Well-Being: Does Selectivity Matter?

Individuals tend to self-report higher well-being levels on certain days of the week than they do on the remaining days, controlling for observables. Using the 2008 release of the British Household Panel Survey, we test whether this empirical observation suffers from selection bias. In other words, we examine if subjective well-being is correlated with unobserved characteristics that lead the individuals to take the interview on specific days of the week. We focus on two distinct well-being measures: job satisfaction and happiness. We provide convincing evidence for both of these measures that the interviews are not randomly distributed across the days of the week. In other words, individuals with certain unobserved characteristics tend to take the interviews selectively. We conclude that a considerable part of the day-of-the-week patterns can be explained by a standard “non-random sorting on unobservables” argument rather than “mood fluctuations”. This means that the day-of-the-week estimates reported in the literature are likely to be biased and should be treated cautiously.