Sensitivity analysis in a multidimensional demographic projection model with a two-sex algorithm

"Formulas are derived for the effect that a slight change in the occurrence/exposure rate of the multidimensional projection model has on the elements of the population vector. The projection model classifies the population by sex, age, and marital status. The model includes a two-sex algorithm in order to ensure consistency between numbers of male and female marriages, number of divorces for the two sexes, and new widows (widowers) and deceased spouses. The sensitivity functions and elasticities are applied to data from the Netherlands for the period 1980-1984. The results indicate that marriage market mechanisms, in particular competition and substitution effects, are reasonably well modelled."     

An alternative formulation of the birth function in a two-sex model

The inconsistency in Lotka's stable population model (two different intrinsic growth rates for the two sexes) arises from the fact that he considers two equations (for male and female births), and not because his equation for one sex does not involve the other. Many authors in the past have erroneously put emphasis on the latter point and modified Lotka's equations for male and female births. Since sex ratio at birth is constant, two independent equations for male and female births cannot exist. The correct approach is to attempt to form an equation for all births. The author followed this approach in his earlier works on the problem, but his birth functions were formulated from axiomatic considerations. The present paper provides a new birth function which has an intuitively appealing physical interpretation, and for which the interaction between the sexes is empirically determined from the data.     

[An analysis of regional differential mortality].]

Regional differences in mortality and life expectancy in China are explored, and the socioeconomic, cultural, and educational factors affecting such differences are considered using data from the 1982 census. The author notes that mortality, particularly infant mortality, is highest in economically underdeveloped areas, and female infant mortality is high in both rural and urban areas. It is also observed that female life expectancy is 3.26 years longer than for males in urban areas, and 1.38 years longer in rural areas.     

Revised regional model life tables at very low levels of mortality

This paper presents and discusses new model life tables at very low mortality, which make use of age-specific death rates from the 1960s, 1970s, and 1980s. These life tables fit recorded death rates in very low mortality populations better than do the existing ones at expectations of life of 77.5 and 80 years. The old tables incorporate too-high mortality at the higher ages and in infancy and they incorporate regional differences that no longer exist. The new tables "close out" the mortality schedules above age 80 more realistically. The convergence of age patterns of mortality at very high life expectancies in populations that used to conform to different families is in itself of demographic interest. Some convergence may perhaps be expected. Sullivan (1973) found that, in Taiwan, the comparison of mortality at ages 1-5 to mortality at 5-35 in the late 1950s showed higher mortality at the younger ages relative to the ensuing 30-year age interval than was found in any of the models, including the South model, which has the highest relative mortality from ages 1-5 among the 4 regional patterns. Then, in the late 1960s, the relation of mortality at 1-5 to mortality at 5-35 in Taiwan fell to a position intermediate between the West and South tables. Sullivan found in data on mortality by cause of death a large reduction in mortality from diarrhea and enteritis, no doubt as a result of environmental sanitation. Mortality from these causes is concentrated among young children, and reduction in deaths from these causes would naturally diminish the excess mortality in this age interval. The East pattern, characterized by very high mortality in infancy (but not from 1-5), may be the result of the prevalence of early weaning or avoidance of breast feeding altogether in the populations characterized by this pattern. As health conditions have improved, evidenced by the overall design of mortality, these special factors are diminished or erased. Model life tables at these very low mortality levels have different uses from most applications of model life tables at higher mortality. The use of model tables to estimate accurate schedules of mortality when the basic data are incomplete or inaccurate is less relevant in this range of mortality levels.     

An equity-based model of vandalism

An equity-based model of vandalism is proposed which views this behavior as often having meaning for vandals and for society. Type and intensity of vandalism are then predicted based upon a specification of first and second order moderators of inequity resolution, and an ordering of vandalism along dimensions of instrumentality, expressiveness and message ambiguity. The role of perceived control as a primary determinant of mode and intensity of vandalism is stressed. Second order moderators such as state of the physical environment and availability of various group level processes are also incorporated into the model as sufficient, but not necessary, conditions. Illustrative predictions include the occurence of diffuse, malicious vandalism when inequity is high and control is low; whereas more tactical-selective forms of vandalism are proposed when control approaches moderate levels.Requests for reprints should be sent to Dr. Jeffrey D. Fisher or Dr. Reuben M. Baron, Department of Psychology, U-20, University of Connecticut, Storrs, CT 06268.     

The integrative potential of a fertility model: An analytical test

Abstract In an earlier paper a working model of marital fertility was presented.(1) That model grew out of a close study of Becker's economic model for fertility analysis.(2) Becker's model was modified in several respects in order to meet a number of major objections levelled against it by Judith Blake, Deborah Freedman, and others.(3) The purpose of the present paper is to examine how far the model presented earlier can serve as a 'binder' for the interpretative schemes now available in the literature on fertility differentials. More specifically, the objective is to identify the underlying explanatory factors of a number of analytical hypotheses concerning fertility differentials, and to examine whether the factors thus identified can be located in the fertility model presented in the earlier paper.(4) Little attention will be paid to the causal directions, if any, recognized in the hypotheses studied, nor will we attempt to provide a systematic review of empirical findings.     

On the validity of MAPE as a measure of population forecast accuracy

The mean absolute percent error (MAPE) is the summary measure most often used for evaluating the accuracy of population forecasts. While MAPE has many desirable criteria, we argue from both normative and relative standpoints that the widespread practice of exclusively using it for evaluating population forecasts should be changed. Normatively, we argue that MAPE does not meet the criterion of validity because as a summary measure it overstates the error found in a population forecast. We base this argument on logical grounds and support it empirically, using a sample of population forecasts for counties. From a relative standpoint, we examine two alternatives to MAPE, both sharing with it, the important conceptual feature of using most of the information about error. These alternatives are symmetrical MAPE (SMAPE) and a class of measures known as M-estimators. The empirical evaluation suggests M-estimators do not overstate forecast error as much as either MAPE or SMAPE and are, therefore, more valid measures of accuracy. We consequently recommend incorporating M-estimators into the evaluation toolkit. Because M-estimators do not meet the desired criterion of interpretative ease as well as MAPE, we also suggest another approach that focuses on nonlinear transformations of the error distribution.     

[An inquiry concerning the birth model].]

The author modifies the parity progression model of fertility by using the parity progression ratio as a control indicator of fertility. A regression equation is used to calculate the total fertility rate for China at parity one.     

An exponential model of female sterility

It is suggested that a useful component of a fertility simulation would be proportions of females sterile by age. Data on this phenomenon are rather limited, but they indicate that proportional sterility may not easily be described by a simple function. We propose that rates of becoming sterile may be adequately described by an exponential function utilizing proper parameter values. Such exponential-model rates form the basis for computation of a fecundity decrement table presented in this paper. Sterility proportions from the table are compared to some empirical data.     

An assessment of the own-children method of estimating fertility by birthplace in Australia

This paper examines the validity of the own-children method of fertility estimates derived from the 1991 Census by a detailed investigation of mortality assumptions, the presence of non-own children, age misreporting and undercount. A comparison of fertility measures derived alternatively from the census using the own-children method and from vital statistics for the period 1987–91 indicates remarkably similar rates for Australia-born women, and plausible results for long established migrant groups. The own-children fertility levels for some recently arrived migrant groups, however, were found to be misleading. It is suggested that the own-children method is useful for the study of differential current fertility in Australia. Revised version of an essay awarded the W.D. Borrie Prize (graduate section), 1997, and presented to the session: Advances in methods for the analysis of demographic data of the 23rd General Conference of the International Union for the Scientific Study of Population, 11–17 October, Beijing. This paper is based on the author’s PhD thesis entitled:Fertility patterns of Australian selected immigrant groups, 1977–91.     

An economic model of teenage pregnancy decision-making

In this paper, we model unmarried teenagers' decisions about their pregnancy outcome by considering that the teenager contrasts her expected utility (1) as a married mother, (2) as an unmarried mother, or (3) after abortion. We use cross-sectional data on 297 California teenagers aged 13-19 who were pregnant for the first time between 1972 and 1974. Both Anglo and Mexican-American girls are included. We find that pregnant girls who are eligible for or are receiving public assistance are more likely to give birth and remain unmarried. Teenagers with greater time values are more likely to choose abortion, and Mexican-American girls are more likely to carry their pregnancies to term.     

Sixty years of change in Tibetan fertility: An assessment

Existing knowledge of Tibetan historical population development is mostly based on ‘best-guess’ estimates and is heavily politicized. Using census data, I reconstruct the development of Tibetan fertility in China since the 1940s, with the objective of providing an independent assessment that can be used as benchmark for future studies and debates on Tibetan demography. Following major social and economic transformations starting in the 1950s, Tibetan fertility unexpectedly increased from the late 1950s to the late 1960s. As noted in several existing studies, Tibetan fertility in China then declined swiftly from the early 1980s onwards and has now reached values close to replacement level. Focusing on the 1950–70 period, I examine factors that contributed to shaping the Tibetan fertility increase in more detail. This confirms that changes in nuptiality and disease-related infertility both played a role in pushing up fertility rates among Tibetan women in China.     

An interpretive review of women's experiences of gestational diabetes mellitus: Proposing a framework to enhance midwifery assessment

BackgroundGestational diabetes mellitus (GDM) affects almost 5% of pregnancies in Australia, and within 15 years, 25% of affected women will go on to develop Type 2 Diabetes Mellitus (T2DM). The adoption of preventive health behaviours may be influenced by women's experiences of GDM.QuestionThis review sought to understand women's beliefs, values, perceptions and experiences following diagnosis of GDM.MethodsPeer reviewed and professional journals were searched for primary research, published between January 1991 and December 2011 that explored the beliefs, values, perceptions and experiences of peripartum or postpartum women with a diagnosis or history of GDM.FindingsNineteen studies met the inclusion criteria and the majority of these studies were qualitative (n = 15). Each study was reviewed and synthesis revealed three emergent themes and core concepts related to each theme: Responses (initial reaction to GDM diagnosis, negative thoughts following diagnosis, struggle to manage GDM, feelings of ‘loss of control’, changes to identity and adapting to change), Focus of Concern (concern for baby's health, mother's concern for her own health, perceived seriousness of GDM, perceived fear of T2DM) and Influencing Factors (cultural roles and beliefs, social stigmas, social support, professional support, adequate and appropriate information, social roles and barriers to self-care).ConclusionThe experiences of women with GDM are unique and personal however this review highlights common experiences evident in the existing research. The proposed framework may be used by midwives in clinical assessment and care of women diagnosed with GDM.     

[Estimating the error of random projection of discrete populations].]

The author estimates the error of stochastic projection of discrete populations by defining fertility and mortality as stochastic processes. Using Chebyshev's inequality and data for Huzhou City's population, the author estimates random fluctuations of fertility and mortality and develops an equation for estimating the relative error of projection of total population.