Scenario Analysis in Population Projection

This paper focuses on the approach to population projections that has been labeled scenario analysis. It looks at the original meaning of "scenario" and then discusses its appropriate usage in population projections with respect to several criteria, especially that of consistency of assumptions. Next, the paper describes the practical considerations and actual experiences in an IIASA effort to define alternative scenarios for 12 world regions to the year 2030 through discussions of a group of experts. Because of differential expertise and an uneasiness of experts to numerically define alternative scenarios, an interactive group process was chosen rather than a larger Delphi. On practical and theoretical grounds it became apparent that individual responsibility and judgement of the authors cannot be replaced by an anonymous "objective" entity making the assumptions. Finally, the paper discusses what kind of alternative variants (or scenarios) the users can handle and do expect. It is exemplified through the specific question whether the UN should change its current practice of making population projections. Pro and contra arguments are listed concerning the proposal to include alternative mortality assumptions into the three main variants that are widely publicized

On the Concentration of Childbearing in China, 1955-1981

Based on period parity progression ratios derived from the one-per-thousand fertility survey by Feeney and Yu (1987) completed parity distributions implied by period fertility are calculated for the years 1959-1981. Concentration analysis of these distributions using Lorenz curves and the proportion of women that had half the children was almost invariant over time (around 33%-35%) despite the dramatic fertility decline since the mid 1960s. This is in sharp contrast to a great number of other countries where the fertility transition has been accompanied by sharply increasing concentration. The very egalitarian way in which fertility declined in the Chinese population seems to be a unique case in world history

Toward a Systematic, Argument-Based Approach to Defining Assumptions for Population Projections

This paper proposes a new approach for defining the assumptions in population projections. It is based on a broad discussion and argumentation exercise which critically assesses the science basis of alternative arguments that relate to the forces which jointly shape the future trends in fertility, mortality and migration. It starts by discussing the results of a recent Eurostat survey among all EU national statistical offices in which there appears a clear consensus that the current practice of defining assumptions for population projections should be improved through stronger interactions with the scientific community. As an instrument for such interactions, the paper goes on to propose an interactive spreadsheet in which more than 100 arguments relating to the forces shaping future fertility, mortality and migration have been formulated. Invited experts then evaluate these arguments with respect to their validity and their potential impacts on the force under consideration. This interactive questionnaire has already been used to define the assumptions in the official UK population projections and with an international group of 17 mortality experts. With further fine tuning, this approach can be used to collect and synthesize the expertise of large numbers of experts for defining median assumptions and the associated ranges of uncertainty. It has the potential to become a standard tool for the future production of national and international population projections

A QM/MM equation-of-motion coupled-cluster approach for predicting semiconductor color-center structure and emission frequencies

Valence excitation spectra are computed for all deep-center silicon-vacancy defect types in 3C, 4H, and 6H silicon carbide (SiC) and comparisons are made with literature photoluminescence measurements. Nuclear geometries surrounding the defect centers are optimized within a Gaussian basis-set framework using many-body perturbation theory or density functional theory (DFT) methods, with computational expenses minimized by a QM/MM technique called SIMOMM. Vertical excitation energies are subsequently obtained by applying excitation-energy, electron-attached, and ionized equation-of-motion coupled-cluster (EOMCC) methods, where appropriate, as well as time-dependent (TD) DFT, to small models including only a few atoms adjacent to the defect center. We consider the relative quality of various EOMCC and TD-DFT methods for (i) energy-ordering potential ground states differing incrementally in charge and multiplicity, (ii) accurately reproducing experimentally measured photoluminescence peaks, and (iii) energy-ordering defects of different types occurring within a given polytype. The extensibility of this approach to transition-metal defects is also tested by applying it to silicon-substitutional chromium defects in SiC and comparing with measurements. It is demonstrated that, when used in conjunction with SIMOMM-optimized geometries, EOMCC-based methods can provide a reliable prediction of the ground-state charge and multiplicity, while also giving a quantitative description of the photoluminescence spectra, accurate to within 0.1 eV of measurement in all cases considered.Comment: 13 pages, 4 figures, 6 tables, 5 equations, 100 reference

Culture, Religion and Fertility: A Global View

This study tries to assess the effects of culture and religion on fertility after accounting for a country's socio-economic standing. Analysis of covariance models are estimated for 128 countries with time-series covering the period 1950-75. The dependent variable is the gross reproduction rate; independent variables are the infant mortality rate, an aggregate indicator of female educational standing, and GDP per caput as well as categorial variables for religion and cultural region. It turns out that the European countries have generally lower fertility than could be expected from their socio-economic standing. In the Arabic countries culture and religion tend to have strong positive effects on fertility. Across cultures Catholicism has a fertility-increasing effect but it is--like the effect of all religions except Islam--diminishing over time. In contrast, the effect of culture (as measured by a regional variable) on the level of national fertility has been increasing at the expense of socio-economic effects

Demographic Metabolism: A Theory of Socioeconomic Change with Predictive Power

Inspired by the work on social change through generational/cohort replacement of Karl Mannheim and Norman Ryder - who coined the notion of Demographic Metabolism - this paper suggests the application of the methods of multi-dimensional mathematical demography to forecast the changing composition of the population by relevant individual characteristics that go far beyond the traditional age, sex and place of residence. It is claimed that unlike many so-called theories in the social-sciences - which mostly are classification schemes - this model actually meets the falsifiability criteria of Popper and Lakatos that the latter distinguishes a theory from "pseudoscience." As presented here, this theory can make quantitative predictions of socioeconomic change with only a narrow margin of uncertainty for decades into the future. The paper gives two very different examples of predictions based on this theory: one for the hard and sticky characteristic of highest educational attainment where higher human capital of the future labor force is safely predicted for countries that recently experienced expansions in school enrollment and another for the soft and more volatile characteristic of European identity which shows significant inter-cohort increases that will likely result in a higher future prevalence of a European identity in addition to a national one among the electorate of the EU. This new theory has the potential to finally providing the social sciences with a paradigm with true (quantitative) predictive power for decades into the future