Pre‐procreative ages in population stability and cyclicity

Age‐specific models of population renewal (with and without feedback) which imply convergence to a stable state for some levels of fertility or feedback may imply the presence of long‐term cycling around a constant or exponentially changing equilibrium for other levels of fertility or feedback. The switch from one regime to the other is a “bifurcation.”; The conditions for bifurcation involve the roots of an analogue of Lotka's Equation.

Typically bifurcation is induced by raising the strength of feedback or the level of fertility. It has been known since the early 1980s, however, that this is sometimes impossible. It is sometimes impossible even with the linear renewal equation itself and with the most basic of non‐linear models, Lee's cohort feedback model.

Here it is proved that this typical route to bifurcation does not fail for these basic models in the presence of a condition which always holds for realistic applications with higher organisms: the existence of a span of ages before the onset of fertility.

Specifically, a strictly positive lower bound on ages of procreation is proved to be sufficient to guarantee the existence of a rescaling of Lotka's Equation for which the real part of some complex root vanishes. This result holds for absolutely Lebesgue‐integrable (signed) net maternity functions on the positive real line and for absolutely summable (signed) net maternities on the positive integers.

It follows that Coale's rescaling device for the analysis of approach to stability in stable population theory can be implemented for all realistic human net maternity schedules. It also follows that the many special cases of the cohort feedback model throughout population biology will all generate persistent cycling instead of stability if feedback is sufficiently strong.     

Correlation bias in U.S. census adjustment

One form of error that can affect census adjustments is correlation bias, reflecting people who are doubly missing--from the census and from the adjusted counts as well. This article presents a method for estimating the total national number of doubly-missing people and their distribution by race and sex. Application to the 1990 U.S. census adjustment leads to an estimate of 3 million doubly-missing people. Correlation bias is likely to be a serious problem for census adjustment in 2000. The methods of this article are well suited for measuring its magnitude.     

Communicating future water needs to an at-risk population: lessons learned following defeat of the Applewhite Dam and Reservoir Project in San Antonio,Texas

San Antonio, Texas, the seventh largest city in the United States, has experienced steady population growth, since the “boom” of the 1960s. Projected water shortages due to this growth were realized as early as the 1970s by city leaders and south-central Texas regional development decision makers. To reduce dependence on the already over-taxed, Edwards aquifer, a solution, the Applewhite Dam and Reservoir Project, was developed with wide acceptance by federal, state, and city leaders who regarded the project as a necessary measure for regional growth and development. However, opposition by taxpayer and environmental groups led to referendums of 1991 and 1994 in which voters blocked construction of the dam and reservoir leaving the city with limited options for water provision. This case study investigated the factors which led to a clear mismatch in communication between decision makers—those who were aware of the actual and quantifiable risk to the region in terms of reduced water supplies—and the general public, a population that did not have complete and/or adequate knowledge of their actual risk regarding future water shortages, nor, of solutions being developed, such as the Applewhite project. The findings from this case study indicate that when municipal leadership fails to adequately communicate risk regarding resource shortage to an affected public, as well as, openly planned solutions, that voters are likely to underestimate future impacts of water shortages, heed last-minute opposition, and reject long-standing, publicly proposed projects. The intent of this research is not to support either side in the Applewhite controversy, but to shed perspective on the process of adequately and effectively communicating future water needs to an at-risk population. Decision makers in cities across the United States who are faced with solving problems of limited resources needed by a large populace may be informed by the results of this research.     

Evaluating the slavonian census of 1698 part II: A microsimulation test and extension of the evidence

An adjusted 17th C. census based on critical reading of the historical text is the basis for indirect estimation of uncounted persons. The census states no ages and excludes many categories of household residents. Microsimulation based on historically and ethnographically plausible rates and household formation scenarios produces simulated households that match the observable portions of households in the adjusted census. Microsimulation results permit estimation of the uncounted population, of the kinship and age composition of households under extant frontier conditions, and the probable future composition of households as the frontier stabilized and land shortage began to exert pressure for greater density and household complexity.     

Settlement Intentions and Immigrant Integration: The Case of Recently Arrived EU‐Immigrants in the Netherlands

The aim of this study is to examine the effect of settlement intentions on the integration of recently arrived EU‐immigrants in the Netherlands. Hypotheses on differences in integration, both shortly after arrival and over time, are derived from the intergenerational immigrant integration model. Based on two waves of the New Immigrants to the Netherlands Survey, a longitudinal multilevel model was estimated. Most differences were found with regard to the level of integration shortly after arrival. Immigrants who intended to stay had more contact with natives, were more proficient in Dutch, and consumed more host country media than immigrants who intend to leave. On the other hand, they worked fewer hours per week than immigrants who intend to leave. Differences over time were only found with regard to Dutch language proficiency: immigrants who intend to stay increased their proficiency more strongly than immigrants who intend to leave.     

Judging unions’ future using a historical perspective: the public policy choice between competition and unionization

VII. Conclusion In discussing the future of private sector union membership one needs to evaluate the early period of union ascendancy (1930s through the early 1950s) as well as the past few decades when unions have been in decline. We know trends currently in place are unfavorable to unions. What conditions would be favorable? When the earlier period of union growth us studied, two factors become prominent — the competitiveness of the labor market and the ability of unions to fullfill their major goal of either extracting economic rents or remedying market failures that result in exploitive employment relationship.     

Relationships between period and cohort life expectancy: Gaps and lags

This paper offers an empirical and analytic foundation for regarding period life expectancy as a lagged indicator of the experience of real cohorts in populations experiencing steady improvement in mortality. We find that current period life expectancy in the industrialized world applies to cohorts born some 40–50 years ago. Lags track an average age at which future years of life are being gained, in a sense that we make precise. Our findings augment Ryder's classic results on period–cohort translation.     

Pre-procreative ages in population stability and cyclicity

"Humans' protracted maturation before childbearing is an extreme example of a general characteristic of higher organisms: a positive lower bound on ages of procreation. The pre-procreative span, much discussed for its evolutionary and social ramifications, has consequences also for the mathematics of population renewal....This paper proves the presence of a pre-procreative span sufficient, in and of itself, to guarantee the existence condition for bifurcation for all models in one important class. The class includes the best-studied examples of age-specific systems with and without homeostatic feedback in purely discrete and in purely continuous formulations."     

Ergodicity and Inverse Projection

Examination of the responses of vital rates to variations in grain prices in nine pre-industrial European countries confirms the existence of the short-term Malthusian preventive and positive checks. The structure and magnitude of the preventive check are strikingly similar in all countries and all periods. On the other hand, the strength of the positive check varies widely and in remarkable accord with measures of economic development. The size of the positive relative to the preventive check diminishes as economic development increases. Among the countries examined, differences in the response of population growth rates to price fluctuations can be attributed primarily to differences in the strength of the positive check.     

A probability model for census adjustment

The census can be adjusted using capture‐recapture techniques: capture in the census, recapture in a special Post Enumeration Survey (PES) done after the census. The population is estimated using the Dual System Estimator (DSE). Estimates are made separately for demographic groups called post strata; adjustment factors are then applied to these demographic groups within small geographic areas. We offer a probability model for this process, in which several sources of error can be distinguished. In this model, correlation bias arises from behavioral differences between persons counted in the census and persons missed by the census. The first group may on the whole be more likely to respond to the PES: if so, the DSE will be systematically too low, and that is an example of correlation bias. Correlation bias is distinguished from heterogeneity, which occurs if the census has a higher capture rate in some geographic areas than others. Finally, ratio estimator bias and variance are considered. The objective is to clarify the probabilistic foundations of the DSE, and the definitions of certain terms widely used in discussing that estimator.