Food Security, Fertility Differentials and Land Degradation in Sub-Saharan Africa: A Dynamic Framework

We study the impact of differential fertility levels for the food-insecure and food-secure population on the long-run values of the population distribution and resources in a descriptive model where the food security states are determined by a historically given food distribution and the endogenous food production with resources and labour as inputs. Furthermore, we assume that the resource stock is reduced by poverty-driven environmental degradation. Moreover, we incorporate nutritional effects on labour productivity and mortality. By applying local bifurcation theory, we show that the model may exhibit multiple equilibria. Furthermore, the orbits of resources and the population distribution may be characterised by quasi-periodic behaviour. Sustainable development in terms of approaching a steady state with positive values of resources and food-secure population is only promoted by low fertility levels of the food-insecure and food-secure population.

Contribution of the Rise in Cohabiting Parenthood to Family Instability: Cohort Change in Italy, Great Britain, and Scandinavia

In this study, we investigate through microsimulation the link between cohabiting parenthood and family instability. We identify mechanisms through which increases in cohabiting parenthood may contribute to overall increases in separation among parents, linking micro-level processes to macro-level outcomes. Analyses are based on representative surveys in Italy, Great Britain, and Scandinavia (represented by Norway and Sweden), with full histories of women's unions and births. We first generate parameters for the risk of first and higher-order birth and union events by woman's birth cohort and country. The estimated parameters are used to generate country- and cohort-specific populations of women with stochastically predicted family life courses. We use the hypothetical populations to decompose changes in the percentage of mothers who separate/divorce across maternal birth cohorts (1940s to 1950s, 1950s to 1960s, 1960s to 1970s), identifying how much of the change can be attributed to shifts in union status at first birth and how much is due to change in separation rates for each union type. We find that when cohabiting births were uncommon, increases in parents' separation were driven primarily by increases in divorce among married parents. When cohabiting parenthood became more visible, it also became a larger component, but continued increases in parents' divorce also contributed to increasing parental separation. When cohabiting births became quite common, the higher separation rates of cohabiting parents began to play a greater role than married parents' divorce. When most couples had their first birth in cohabitation, those having children in marriage were increasingly selected from the most stable relationships, and their decreasing divorce rates offset the fact that increasing proportions of children were born in somewhat less stable cohabiting unions

On the age dynamics of learned societies - taking the example of the Austrian Academy Sciences

In a hierarchical organisation of stable size the annual intake is strictly determined by the number of deaths and a statutory retirement age (if there is one). In this paper we reconstruct the population of the Austrian Academy of Sciences from 1847 to 2005. For the Austrian Academy of Sciences we observe a shift of its age distribution towards older ages, which on the one hand is due to rising life expectancy, i.e., a rising age at death, as well as to an increased age at entry on the other hand. Therefore the number of new entrants has been fluctuating considerably - especially reflecting several statutory changes - and the length of tenure before reaching the age limit has declined during the second half of the last century. Based on alternative scenarios of the age distribution of incoming members - including a young, an old, the 'current' and a mixed-age model - we then project the population of the Austrian Academy and its ageing forward in time. Our results indicate that the 'optimum policy' would be to elect either young or old aged new members.

The impact of policies influencing the demography of age-structured populations: lessons from academies of sciences

In this paper, we assess the role of policies aimed at regulating the number and age structure of elections on the size and age structure of five European Academies of Sciences. We show the recent pace of ageing and the degree of variation in policies across them and discuss the implications of different policies on the size and age structure of academies. We also illustrate the potential effect of different election regimes (regimens? types?) (fixed vs. linked) and age structures of elections (younger vs. older) by contrasting the steady-state dynamics of different projections of Full Members in each academy into 2070 and measuring the size and age-compositional effect of changing a given policy relative to a status quo policy scenario. Our findings suggest that academies with linked intake (i.e., where the size of the academy below a certain age is fixed and the number of elections is set to the number of members becoming that age) may be a more efficient approach to curb growth without suffering any aging trade-offs relative to the faster growth of academies electing a fixed number of members per year. We further discuss the implications of our results in the context of stable populations open to migration

Monthly Estimates of the Quantum of Fertility: Towards a Fertility Monitoring System in Austria

Short-term variations in fertility and seasonal patterns of childbearing have been of interest to demographers for a long time. Presenting our detailed study of period fertility in Austria since 1984, we discuss the problems and advantages of constructing and analysing monthly series of various period fertility indicators that reflect real exposure and potentially minimise the distortions caused by changes in fertility timing. We correct monthly birth data for calendar and seasonal factors and show that seasonality of births in Austria varies by birth order. Our study suggests that most of the timing distortions can be eliminated when using an indicator derived from the period parity progression ratios based on birth interval distributions, termed the "period average parity" (PAP). We illustrate the insights gained with the PAP and compare this with the commonly used total fertility rates in an analysis of the recent upswing in period fertility, starting in the late 2001. This investigation will be useful in establishing a monitoring of monthly fertility rates in Austria.

On the age dynamics of learned societies— taking the example of the Austrian Academy of Sciences

In a hierarchical organisation of stable size the annual intake is strictly determined by the number of deaths and a statutory retirement age (if there is one). In this paper we reconstruct the population of the Austrian Academy of Sciences from 1847 to 2005. For the Austrian Academy of Sciences we observe a shift of its age distribution towards older ages, which on the one hand is due to rising life expectancy, i.e., a rising age at death, as well as to an increased age at entry on the other hand. Therefore the number of new entrants has been fluctuating considerably—especially reflecting several statutory changes—and the length of tenure before reaching the age limit has declined during the second half of the last century. Based on alternative scenarios of the age distribution of incoming members— including a young, an old, the ‘current’ and a mixed-age model—we then project the population of the Austrian Academy and its ageing forward in time. Our results indicate that the ‘optimum policy’ would be to elect either young or old aged new members

Simulating family life courses: An application for Italy, Great Britain, Norway, and Sweden

Background: Family patterns in Western countries have changed substantially across birth cohorts. The spread of unmarried cohabitation, the decline and postponement of marriage and fertility, and the rise in nonmarital births, partnership instability, and repartnering lead to an increasing diversity in family life courses. Objective: In this paper we demonstrate how to set up a tool to explore family life trajectories. This tool models the changing family patterns, taking into account the complex inter-relationships between childbearing and partnership processes. Methods: We build a microsimulation model parameterised using retrospective partnership and childbearing data. The data cover women born since 1940 in Italy, Great Britain, and two Scandinavian countries (Norway and Sweden), three significantly different cultural and institutional contexts of partnering and childbearing in Europe. Results: We guide readers through the modelling of individual life events to obtain a set of aggregate estimates, providing information on the power, technical structure, and underlying assumptions of microsimulations. Validation of the simulated family life courses against their real-world equivalents shows that the simulations not only closely replicate observed childbearing and partnership processes, but also provide high quality predictions when compared to more recent fertility indicators. Conclusions: Using observed population estimates to systematically validate the results both validates our model and increases confidence that microsimulations satisfactorily replicate the behaviour of the original population. Contribution: We create and validate a microsimulation model that can be used not only to explore mechanisms throughout the family life course but also to set up scenarios and predict future family patterns

The longevity of academicians: evidence from the Saxonian Academy of Sciences and Humanities in Leipzig. Vienna Yearbook of Population Research|Vienna Yearbook of Population Research 2013 11|

This study addresses the mortality of the members of the Saxonian Academy of Sciences and Humanities in Leipzig. In fact, learned societies have been shown to present vanguard groups in the achievement of longevity. We use biographical records from the members of the Saxonian Academy of Sciences from 1846 to 2010 and compare their mortality to German life table estimates, where particularly attention is paid to the mortality differentials between eastern and western Germany. The Saxonian academicians show indeed a higher life expectancy at age 60 than the general German male population, where the latter gap has been widening since the 1950s. Comparing the life expectancy values for the Saxonian academicians to available estimates of various European learned societies yields a similar longevity, suggesting that the survival of the academicians is less determined by national mortality conditions but that academicians rather share a common health advantage