Migration and fuel use in rural Zambia

Population and Environment - What is the effect of migration on fuel use in rural Zambia? Opportunities to increase income can be scarce in this setting; in response, households may pursue a...     

Ecosystem resilience, specialized adaptation and population decline: A modern Malthusian theory

The purpose of this article is to construct a theoretical framework characterizing the interactions among economic development, ecosystem equilibrium and possible population decline, and to discuss the population dynamics in the very long run. In our framework, economic activities bridge population and environment. On the one hand, human beings reform the environment through economic activities; on the other hand, economic activities decrease environmental resilience and increase the possibility of an environmental change in a discontinuous and irreversible pattern, as described in Arrow et al. (1995). Furthermore, a highly developed economy also causes over-specialization of human adaptation, which tends to exaggerate the impact of an environmental change on human population size. Received: 19 January 1999/Accepted: 3 July 1999     

Review of the 1977–87 decade of action to combat desertification

This paper was prepared as an introduction to the symposium,Review of the 1988–87 Decade of Action to Combat Desertification, under the authority and sponsorship of the American Association for the Advancement of ScienceCommittee on Arid Lands.     

An extension of the median test to analysis of variance

In a k-way analysis of variance model, the major concern is testing for main effects and for the presence of interaction between the factors. When the assumptions of normality and equal variances are satisfied, the appropriate test to use is the usual F-test for ANOVA. However, when the normality assumption is not satisfied then a robust or nonparametric test is needed to conduct the analysis. In this paper a nonparametric method based on cell counts is proposed. Each cell is divided into L subcells based on predetermined outpoints and the resulting frequencies are laid out in a contingency table. Then the Pearson x² and tne likelihood ratio tests are performed. A comparison with the classical ANOVA F-test indicates that the proposed method is preferable when the data comes from a thick-tailed highly skewed distribution.     

A network algorithm for the exact treatment of the 2×k contingency table

A common statistical problem encountered in biomedical research is to test the hypothesis that the parameters of k binomial populations are all equal. An exact test of significance of this hypothesis is possible in principle, the appropriate null distribution being a normalized product of k binomial coefficients. However, the problem of computing the tail area of this distribution can be formidable since it requires the enumeration of all sets of k binomial coefficients whose product is less than a given constant. Existing algorithms, all of which rely on explicit enumeration to generate feasible binomial coefficients     

对冲基金吸引大投资者 机构投资者计划向其投入更多资金

一项来自英国非主流投资研究机构Preqin的调查显示，尽管许多投资者纷纷从对冲基金中撤资，机构投资者仍计划向其中投入更多的资金。     

The pattern of birth spacing during Taiwan's demographic transition

This paper considers the impact of an extended family structure on the fertility behavior of married women in Taiwan. A sequential duration model is applied to identify the differences in fertility behavior during the early and latter stages of a woman's reproductive period. Heterogeneity adjustments which correct the respondent-specific characteristics are also implemented. It is found that living with the husband's parents has an impact on the wife's fertility only at the early stage of her childbearing period, and that the subjective son preferences together with the objective fact of no son in the previous 2 births do force a wife to expedite her third birth. These results are robust across different cohorts during the demographic transition and under different specifications of hazard functions. We thank an anonymous referee for his or her valuable comments and suggestions. Responsible editor: Junsen Zhang.     

Vitamin D and the postmenopausal population

Vitamin D, a hormone critical to the body's maintenance of serum calcium and phosphorus concentrations, is currently the subject of much scientific interest. Low levels of vitamin D have been observed in many populations and epidemiological studies have suggested a link between this biochemical state and a range of diseases, such as cancer, diabetes and multiple sclerosis. While the consequence of vitamin D deficiency is well documented for bone (rickets and osteomalacia), with mixed findings relating to falls and fractures, a causal link between vitamin D deficiency and these wider health outcomes has not been established. If these relationships were found to be causal, the morbidity and mortality resulting from low levels of vitamin D could be substantial; the current evidence base, however, most robustly supports the assessment of serum 25(OH)-vitamin D in the context of specific symptoms, low bone mineral density or biochemical abnormalities, rather than as an entity to treat in its own right or as the basis for a population-wide screening programme.     

Coresidence With Elderly Parents: A Comparative Study of Southeast China and Taiwan

Using recent survey data from the Panel Study of Family Dynamics (PSFD) on 1,655 married persons born in 1964-1976 in southeastern China and Taiwan, we studied coresidence with elderly parents using a multinomial probit model for coresidence type and an ordered probit model for residential distance. The study yielded four findings: (a) Patrilocal coresidence was more prevalent in Taiwan than in China; (b) matrilocal coresidence was more prevalent in China; (c) practical factors mattered in both places; (d) in Taiwan only, a couple's economic resources facilitated breaking away from patrilocal coresidence. The findings suggest that, although economic development does not necessarily result in less traditional familial culture, personal economic resources may enable individual couples to deviate from tradition.