Parametric bootstrap goodness-of-fit testing for Wehrly–Johnson bivariate circular distributions

The Wehrly–Johnson family of bivariate circular distributions is by far the most general one currently available for modelling data on the torus. It allows complete freedom in the specification of the marginal circular densities as well as the binding circular density which regulates any dependence that might exist between them. We propose a parametric bootstrap approach for testing the goodness-of-fit of Wehrly–Johnson distributions when the forms of their marginal and binding densities are assumed known. The approach admits the use of any test for toroidal uniformity, and we consider versions of it incorporating three such tests. Simulation is used to illustrate the operating characteristics of the approach when the underlying distribution is assumed to be bivariate wrapped Cauchy. An analysis of wind direction data recorded at a Texan weather station illustrates the use of the proposed goodness-of-fit testing procedure.     

A comparison of soil carbon dynamics in residential yards with and without trees

Residential lawns provide chronosequences to examine influences of home age and aboveground tree biomass (ATB) on soil carbon (C) levels. Soil C dynamics were compared between 44 lawns with trees (LwT) and 23 without trees (PL). At the 0–15 cm depth, LwT had higher mean soil C than PL and an earlier rise in median soil C across home age. Nonparametric quantile regression also showed a steeper rise in the 5th, 50th, and 95th soil C quantiles for LwT. Fitted polynomial regression models indicated that home age and ATB together accounted for 40 % of the soil C variation at the 0–15 cm depth [C = 1.34 + 0.05(Age) + 0.0003(ATB)]. At the 15–30 cm depth, the interaction between home age and ATB explained 33 % of the soil C variation [C = 0.78 + 0.0003(Age*ATB)]; at 30–50 cm, ATB was responsible for 20 % [C = 0.56 + 0.0003(ATB)].     

The analysis of linkages in demographic theory

Many seemingly different questions that arise in the analysis of population change can be phrased as the same technical question: How, within a given demographic model, would variable y change if the age- or time-specific function f were to change arbitrarily in shape and intensity? At present demography lacks the machinery to answer this question in analytical and general form. This paper suggests a method based on modern functional calculus for deriving closed-form expressions for the sensitivity of demographic variables to changes in input functions or schedules. It uses this “linkage method” to obtain closed-form expressions for the response of the intrinsic growth rate, birth rate, and age composition of a stable population to arbitrary marginal changes in its age patterns of fertility and mortality. It uses it also to obtain expressions for the transient response of the age composition of a nonstable population to time-varying changes in the birth sequence, and to age-specific fertility and mortality patterns that change over time. The problem of “bias” in period vital rates is also looked at.     

The Ergodic Theorems of Demography: a Simple Proof

Standard proofs of the ergodic theorems of demography rely on theorems borrowed from positive matrix theory, tauberian theory, and the theory of time-inhomogeneous Markov matrices. These proofs are efficient and expedient, but they give little direct insight into the mechanism that causes ergodicity. This paper proposes a simple and unified proof of the two ergodic theorems. It is shown that the birth dynamics can be decomposed into a smoothing process that progressively levels out past fluctuations in the birth sequence and a reshaping process that accounts for current period-to-period changes in vital rates. The smoothing process, which causes the birth sequence to lose information on its past shape, is shown to be the ergodic mechanism behind both theorems.     

Some general relationships in population dynamics

This paper extends the Lotka system of stable population equations to any population. The authors present this new general system and describe its duality with the recent Preston-Coale system. They derive these results by considering the calculus of change on the surface of population density defined over age and time. They show that analysis of this Lexis surface leads to all the known fundamental relationships of the dynamics of single-region human populations, several interesting new relationships, and a duality between period and cohort life tables.     

Quantifying socio-environmental impacts of predator control policies

Quantitative indices of the socio-environmental impacts of predator control were derived from a mathematical synthesis of public perceptions and physical measures of environmental change. A nationwide survey of the U.S. public yielded cardinal measures of preference for the acceptability, primary and secondary effects on other wildlife, and cost effectiveness of control policies. To determine the public evaluation of a particular policy, the preference values were used to weight social indicators describing the physical impacts of a policy. Policymakers will be able to use the resulting values to view the tradeoffs between economic and socio-environmental costs and benefits of various policy alternatives.     

Fertility decision making,unintended births,and the social drift hypothesis: A longitudinal study

To explore relationships between fertility intentions and subsequent childbearing, data were collected from 334 mothers in a metropolitan area in 1963 and again in 1971, allowing for a time interval of eight years for testing a series of hypotheses on fertility control. The results suggested that social psychological obstacles to decision making should be taken into account as potential qualifiers of the more rational models of fertility behavior currently prevalent in the literature. The alienation variable of meaninglessness was examined in conjunction with education, age at marriage, marital duration, and previous parity. The analyses indicated that pregnancies for many women are experienced as occurrences, happenings, or unintended events within a social psychological context of social drift.Research support pursuant to contract NIH-71-2028 with the Center for Population Research, NICHD, is gratefully acknowledged, as is the assistance of David W. Chilson in the processing of the data. Request reprints from either author, Sociology Department, Bowling Green University, Bowling Green, Ohio 43403.     

The Socioeconomic Attainments of Second-Generation Southeast Asian Americans in the 21st Century: Evidence from the American Community Survey, 2012–2016

Population Research and Policy Review - Although decades have passed since the initial immigration of Southeast Asians to the U.S. after the Vietnam War, the socioeconomic outcomes of the...     

The role of savings and wealth in reducing ‘wilt’ between expectations and college attendance

‘Wilt’ occurs when a young person in high school expects to attend college but does not do so shortly after graduating. In this study we find that youth with no savings account in their own name are more likely to experience wilt than any other group examined. In multivariate analysis, young people who expect to graduate from a four-year college and have an account are approximately six times more likely to attend college than those with no account. Teens who expect to graduate from a four-year college and have designated a portion of their savings for college are approximately three times more likely to attend college than those with no account. Additionally, when savings are taken into account, academic achievement is no longer a significant predictor of college attendance. Policy implications are discussed.