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Population projections rely on one-sex renewal models. Consequently, changing the projection of male mortality does not affect the projection of birth, contradicting commonsense. A two-sex renewal model is presented in this paper to provide a better description of reproduction and more reasonable population projections. This model is nonlinear and includes the one-sex renewal models as special cases. In this model, age-specific birth rates are defined for two sexes jointly; total fertility, net reproduction rate, and intrinsic growth rate are also derived for two sexes jointly; and age-specific populations approach or converge to stable status. Applying the two-sex renewal model to Australia, it indicates that one-sex models underestimated the intrinsic growth rate by 14 percent. Compared to the results of one-sex models, the two-sex model would provide higher growth rate for low-fertility countries, and lower growth rate for high-fertility countries. In other words, the one-sex models are commonly biased. If the two-sex model is applied to all the countries, it would project smaller populations for the world in the future. • A two-sex renewal model is presented to provide population projections. [ABSTRACT FROM AUTHOR]

The issues of the existence and uniqueness of estimates of the population growth parameter (Malthusian parameter) and life expectancy of the elderly population in the model of a stable population with an endogenous growth parameter are considered and positively resolved. The results obtained indicate the possibility of estimating the growth parameter, provided that the initial data are smooth, according to an exact general ratio, without using optimization and iterative procedures. The results obtained have both theoretical and practical significance in assessing the life expectancy and mortality of the elderly population. [ABSTRACT FROM AUTHOR]

A standard assumption in integrated assessment models of climate change is that population and productivity are growing, but at a decreasing rate. We explore the signifcance of the assumption of population and productivity growth for greenhouse gas abatement. After all, there has been no long run slow down in the growth of productivity over the past few centuries, and the rate of population growth has actually been increasing for the past 19 centuries. Even if either of these growth rates were expected to slow, by how much is subject to great uncertainty. We show computationally that such continued growth greatly increases the severity of climate change. Indeed we nd that climate change is a problem in large part caused by exogenous population and productivity growth. Rapid reductions in growth make climate change a small problem; smaller reductions in growth imply climate change is a very serious problem indeed. Analogously, reductions in the growth rate of population can be effective in controlling climate change.

First, we consider items that are incepted into operation having already a random (initial) age and define the corresponding remaining lifetime. We show that these random variables are identically distributed when the age distribution is equal to the equilibrium distribution of the renewal theory. Then we consider real populations of items that were incepted into operation (were born) at different instants of time and obtain some useful inequalities between the population age and the remaining lifetime using reasoning similar to that employed in population studies. We also discuss the aging properties of populations using different stochastic orders. [ABSTRACT FROM AUTHOR]

The reproduction and population growth parameters of Anisopteromalus calandrae (Howard) on the 4th instar larvae of Callosobruchus maculatus (Fabricius) were investigated at temperature of 25 ± 1ï°C, 20 ± 5% R.H. and a photoperiod of 16: 8 (L: D) hours. Since the parasitoid eggs are laid inside the seeds where the host larvae live, egg hatch rate (hx) was assumed to be 1 (100%). As a result of this study, the gross and net fecundity and fertility rates were determined to be 306.51 and 236.25, respectively. The average number of eggs produced per female per day was obtained 11.48. The intrinsic and finite rates of increase on the 4th instar of C. maculatus were 0.163 and 1.18, respectively. The mean generation and doubling times were 35.30 and 4.24 days, correspondingly. The gross and net reproduction rates were 123.36 and 109.49 females/female/generation, respectively. The results of this study on the stable age distribution showed that 62.3 % and 37.7 % of the population belonged to immature stages and adults, respectively. The possible application of these results for biological control of C. maculatus is discussed.

Livestock population and its structure is the starting point for all development strategies at both micro and macro level, reason for which accurate knowledge of it is one of the main objectives of official statistics in each state. The analysis aims to highlight the major changes produced after the 90s in terms of population of Bacău county and its structure, with time effects on economic and social activity. Both the 2002 and 2011 census, Bacău was top of the list with an absolute decrease of the population. This was a concern as it has emerged over time as a stable phenomenon. The main reason for the decrease was due to external migration of the population and secondly because of the internal migration flows of population moving towards large economic centers in the country and abroad that attract labor. As most of the migrants are young and active age groups, this phenomena has led to an aging population and to imbalances that can be observed in the age pyramid, with negative effects becoming larger in the future.

The last census of 20 October 2011, confirmed the decrease in the stable population in most localities, although this did not occur uniformly across the county. The analysis aims to highlight the stable population evolution in the last two censuses, which mainly led to decreases in existent disparities between localities, to a slight increase of the degree of uniformity in this regard. If in urban areas, all localities have recorded drops, in the rural areas there were 11 localities with population increases, especially large suburban cities. This led to a slight decrease in the degree of variation in the area, from a coefficient of 45,6% at the census of 2002 to 43,4% in 2011 and the reduction in the ratio of the largest and smallest area, from 7,84 times to 6,08 times. If in 2002 there were 21 local rural residents under 3000 inhabitants, in 2011 their number increased to 26, while more than 10 thousand people do not exist in any village in the county, compared to 2 as they were at the previous census. Territorial disparities are found also among the population by age, existing only 8 villages where the average age has decreased compared to 2002, these being mainly poor localities from Valea Siretului, where the birth rate is higher.

We consider items that are incepted into operation having already a random (initial) age and define the corresponding remaining lifetime. We show that these lifetimes are identically distributed when the age distribution is equal to the equilibrium distribution of the renewal theory. Then we develop the population studies approach to the problem and generalize the setting in terms of stationary and stable populations of items. We obtain new stochastic comparisons for the corresponding population ages and remaining lifetimes that can be useful in applications. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The choice between population reduction or stable population is a critical issue to China. There are two interpretations of the basic national policy -- "population control." Basically completed theory advocating stable population is based on the idea that "excessive population growth" has been effectively curbed and is supported by the population-environment equilibrium theory,"zero growth-sustainable population theory," "the pressure of constant population-disappeared theory" and the "demographic winter theory." Basically completed theory is not only untenable but actually harmful -- "the constant population-pressure disappears" contributes to misleading results of statistical analysis; "zero growth-sustainable population theory" puts the Chinese nation in a very precarious position; "aging is not the decline of the demographic winter" on the fear syndrome is con{using and misleading; reasonable age structure will generate a "fallacy of composition," and will bring disaster to the country and biosphere. "Far from being completed' emphasizes "population reduction" as the main population development strategy for China. First, land capacity is inversely associated with ecological-environmental stability; a population supported by land productivity does not guarantee continuous equilibrium with the environment. Second, the main issue is scale rather than "equilibrium." The lengths of stable and continuous (exponentially decreasing or increasing) Systems with different sizes of population (1. 5 billion or 200 million) are not the same. Third, the size of the population problem has neither economic, system solution, there was no time to save the nature and dissipation point, matter, energy savings technology solutions-technology "ceiling effect," will enable the technology to solve the "stuck" scale quagmire evolved into the "trap" and "black hole." Fourth, a small population and expansive land is what makes the USA such a dominant world power. Russia's rise, in addition to its huge amount of oil and gas, can also be attributed to its small population. Fifth, a large scale population not only constitutes the biggest food security challenge for China and presents a persistent threat, but it also reduces the flexibility of the world grain markets to adjust the economic structure. Sixth, "two different choices, two different destinies." Maintaining a "stable population" of 1.5 billion people is certain to bog China down and may result in the demise of the nation. However, a small-scale population that exhibits the advantages of a smaller demographic base will fundamentally change the basic national conditions of a China plagued by a large population but a weak economic foundation. It would help to ensure food security, increase options and flexibility, and would allow for sustainable development. [ABSTRACT FROM AUTHOR]

It is generally thought that for sake of consistency men and women must have the same average number of lifetime partners. However, this is not the case in general. When men have younger partners, women enter sexual relationships more quickly than men and have a higher number of lifetime partners. A male dominant model applied to UK data on the male rate of entry into a sexual relationship and the male partnership formation function shows that in a stationary population (zero growth rate) women have 9.1% more partners than men. In a stable population with an intrinsic growth rate of -2% and a larger but still plausible difference between the ages of partners, women have 24.6% more partners than men. Given that in sex surveys men report more partners than women, the resulting bias in estimated numbers of partners may therefore be larger than previously thought. [ABSTRACT FROM AUTHOR]

The note attempts to address concerns expressed by Bacaër and Abdurahman (J Math Biol, 2008) in this journal about the definition of generalized reproductive value (RV) as proposed by Ediev (Theor Popul Biol 72(4):480–484, 2007). [ABSTRACT FROM AUTHOR]

A continuous time two-sex stable population model that does not recognize age is examined under the 'harmonic mean' consistency condition of equation (2). Solutions for the stable population intrinsic growth rate r and the sex composition 5 are presented in equations (5) and (6). The process of stabilization is examined, and it is shown that, given two basic constraints, any initial population sex composition will eventually converge to the stable population value. An algebraic solution for the discrete case where the sex ratio at birth is unity is presented and used to describe the trajectory to stability of several hypothetical populations. A closed form algebraic expression for the trajectory to stability is presented for the continuous model in the special case of no mortality. [ABSTRACT FROM AUTHOR]

Montserrat, a small Caribbean island, has maintained a relatively stable population size for the past 95 years. The size of the population between 1891 and 1986 (except for 1946) has been around 12,000. Such stability is rare, especially for a developing society. This stability is in no small way due to net-migration loss. Indirectly also, emigration has suppressed fertility, aged the population and increased the crude death rate. Montserrat's relatively high quality of life is in part a consequence of this relative stability in the size of the population over the last one hundred years. [ABSTRACT FROM AUTHOR]

The age-parity-nuptiality models so far developed by demographers had one or more restrictions on marital status or on the occurrence of births in different marital states. This paper presents a method of constructing a life table incorporating marital status and parity, and develops the age-parity-nuptiality-specific stable population model recognizing all types of marital status, and births to women in any marital status. A method of projecting age-parity-nuptiality-specific distribution of population has also been presented. The proposed model is applied to the United States female population for the year 1970. [ABSTRACT FROM AUTHOR]

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The age-specific growth function of an observed population and the reproductive value function based on the population's current vital rates determine the intrinsic rate of growth implied by those vital rates through the simple relationship given in equation (1). That equation establishes the analytical significance of age-specific growth, and leads to relationships that quantify a population's approach to stability and that specify the extraordinarily close connection between reproductive values and population momentum.

The metastable model generalizes the stable population model by allowing net maternity to change exponentially over age and time. As a result, the metastable model generates an exponentially quadratic birth trajectory, which is characterized by a constant proportion of births by age of mother. The metastable model is well suited to analyzing steady fertility declines and transitions between two regimes of fixed vital rates.

When fertility increases in a previously stable population, the new stable population will be younger than the old one, and the two age distributions will cross at the mean age of the populations.