Generalized Leverage and its Applications

The generalized leverage of an estimator is defined in regression models as a measure of the importance of individual observations. We derive a simple but powerful result, developing an explicit expression for leverage in a general M -estimation problem, of which the maximum likelihood problems are special cases. A variety of applications are considered, most notably to the exponential family non-linear models. The relationship between leverage and local influence is also discussed. Numerical examples are given to illustrate our results     

The problem of defining changes in demographic old age in Poland in a spatial context

The author analyzes the demographic characteristics of the elderly population in Poland. The focus is on the spatial distribution of the elderly around the country.     

宽带卫星通信和星际链路间激光通信的应用前景

提出了由于信息化社会、Ｉｎｔｅｒｎｅｔ、Ｉｎｔｒａｎｅｔ和多媒体技术的出现,从而要求卫星通信向多体制、多功能发展。文中着重分析了具有独特优点的激光通信在宽带卫星通信和星际链路中的现实商用前景。     

Sex preference versus number preference: the case of Korea

The author argues that the effect of sex preference must be disentangled from the effect of number preference in Korea. This study tests--with hazard models--the effect of the number of previous children on the next birth according to the sex composition of previous children. Data were obtained from the 1974 Korean Fertility Survey. This paper also analyzes the timing of childbearing in recent periods in order to determine whether replacement-level fertility is temporary or permanent. The ideal number of children declined from 3.9 children in 1965 to 2.1 in 1991. The age-specific fertility rates for ages 20-24 years declined rapidly during the late 1980s. The fertility rates among women aged 25-29 years and 30-34 years increased during 1985-90. The proportion of fertility among women aged 20-29 years increased from 67.9% in 1975 to 86.6% in 1984. Women born in the late baby boom period of the late 1950s to mid-1960s reached prime reproductive age during the late 1980s and 1990s, but the crude birth rate remained about the same during 1985-92. A higher percentage of women (22.4%) born during 1955-59 remained single in 1990. During 1960-90, the percentage of women aged 20-24 years who were married declined. These trends indicate later age at childbearing and an explanation for the temporary nature of below-replacement fertility in the late 1980s. Korean women did not want to have more than 2 children, and the interval between first and second births increased since 1985. Among pregnancies of parity 2 conceived since 1985, over 90% of women with at least one son ended subsequent pregnancies by abortion compared to only 59% without sons. Hazard models of 1974 data reveal that son preference had an important effect on fertility. Fertility was higher among women with only daughters. Findings suggest that the value of sons must be measured at the societal and not at the individual level.     

獭兔养殖综合技术研究

对獭兔的适应性、饲养管理、疾病防治、产品加工等养殖综合技术进行了研究,提出了獭兔的“三改、两杯、两早一分和两选两适”规范化饲养管理制度和疾病综合防治技术措施,探索出了优质獭兔毛皮和“富钙兔肉脯”的加工工艺以及獭兔良种推广的有效途径。     

Marriage selection and age patterns of mortality: a mathematical investigation

"In this paper, we use simulation models to demonstrate the complexity of the relationship between the marriage selection process and the resulting RMRs [relative mortality ratios]. In particular, we show that marriage selection alone can produce a relative mortality ratio which remains large and relatively constant at ages far beyond the marriage span....Our general objective...is to determine the range of age patterns of relative mortality which could, in theory, result from marriage selection on the basis of health characteristics. We also evaluate the effects of variations in the marriage selection mechanisms on the resulting mortality patterns....We develop and apply several simple mathematical models of the marriage selection process. In order to distinguish the potential consequences of marriage selection from marriage protection, we consider hypothetical populations in which causal effects are absent....We begin by considering an extremely simple marriage selection process and subsequently explore a more realistic selection model based on recent death and marriage rates for Japan."     

Immigration and ethnic origin: the effect of demographic attributes on earnings of Israeli men and women

"The present article examines the separate effects of ethnicity and immigration on earnings by studying a sample of Israeli workers. The results indicate that immigrant status constitutes a major handicap in the Israeli labor market. Ethnicity, on the other hand, plays a minor role in the earnings determination process. The consequences of these results for labor market policies are discussed."     

Major obstacles to control of irregular migrations: prerequisites to policy

This paper examines 3 basic obstacles thwarting all attempts to reduce irregular migration. The 1st, rather well known and analyzed, underscores the dependency of all regulation of migratory flows on the system of economic and political relations between developed and developing countries. The 2nd obstacle resides in the persistance and growth of subsequent dependent irregular migration. This obstacle also reveals the relative autonomy of population movements compared with the employment situation in the labor market. The 3rd generally ignored obstacle is the role played by migration itself, particularly the discriminatory status of foreign workers in the labor market, in producing irregular migration.     

Lactation and fertility in Rural Bangladesh

Summary Analysis of data from various phases of a study of post-partum amenorrhoea in Bangladesh illustrated good aggregate consistency of response on menstrual status, but less individual consistency on duration of post-partum amenorrhoea. Using life table techniques, the median duration of amenorrhoea was calculated as 19.9 months for women with births between February and September 1974. There were substantial seasonal variations in duration, with the median decreasing from 21.5 months for women with February births to 16.9 months for those with September births. By contrast, the median duration of post-partum amenorrhoea varies by only two months for women in the lowest and highest quartiles of weight and weight for height. The seasonal pattern was similar for all weight groups.