A note on unbiasedness in ratio estimation

The method of ratio estimation for estimating the population mean ? of a characteristic y when we have auxillary information on a characteristic x highly correlated with y, consists in getting an estimator of the population ratio R = ?/X? and then multiplying this estimator by the known population mean X?. Though efficient, ratio estimators are in general biased and in this article we review some of the unbiased ratio estimators and discuss a method of constructing them. Next we present the Jackknife technique for reducing bias and show how the generalized Jackknife could be interpreted by the same method.     

中韩出生人口性别比偏高现象之审视

中韩两国在出生人口性别比的变化特点、出生人口性别比偏高产生的原因等方面有着极为相似之处,总结韩国应对出生人口性别比偏高的措施和做法．特别是通过促进妇女政策环境的形成和建立社会性别平等机制来治理出生人口性别比偏高的经验。对于中国具有十分重要的借鉴作用。     

中国流通A股市场投资者实现回报率研究

现实中的股票市场不可能完全符合资本市场有效性假设,因而把股票成交价格看作是股票的市场价值,并据此计算股票投资回报率的传统做法存在着明显的弊端。投资者实际实现的回报率对现实股票市场,特别是规范程度很低的我国股票市场的研究具有重要意义。本文提出了无需完全有效市场假设的现金概念及以此为基础的投资者实现回报率概念,并给出了现有条件下的投资者回报率计算公式和沪深两市的计算结果。     

Sampling design proportional to order statistic of auxiliary variable

The sampling designs dependent on sample moments of auxiliary variables are well known. Lahiri (Bull Int Stat Inst 33:133–140, 1951) considered a sampling design proportionate to a sample mean of an auxiliary variable. Sing and Srivastava (Biometrika 67(1):205–209, 1980) proposed the sampling design proportionate to a sample variance while Wywiał (J Indian Stat Assoc 37:73–87, 1999) a sampling design proportionate to a sample generalized variance of auxiliary variables. Some other sampling designs dependent on moments of an auxiliary variable were considered e.g. in Wywiał (Some contributions to multivariate methods in, survey sampling. Katowice University of Economics, Katowice, 2003a); Stat Transit 4(5):779–798, 2000) where accuracy of some sampling strategies were compared, too.These sampling designs cannot be useful in the case when there are some censored observations of the auxiliary variable. Moreover, they can be much too sensitive to outliers observations. In these cases the sampling design proportionate to the order statistic of an auxiliary variable can be more useful. That is why such an unequal probability sampling design is proposed here. Its particular cases as well as its conditional version are considered, too. The sampling scheme implementing this sampling design is proposed. The inclusion probabilities of the first and second orders were evaluated. The well known Horvitz–Thompson estimator is taken into account. A ratio estimator dependent on an order statistic is constructed. It is similar to the well known ratio estimator based on the population and sample means. Moreover, it is an unbiased estimator of the population mean when the sample is drawn according to the proposed sampling design dependent on the appropriate order statistic.     

社会经济发展与男孩偏好的淡化

本文利用2010年中国人民大学育龄妇女家庭与生育状况调查数据,对男孩偏好弱化现象及导致男孩偏好弱化的社会经济因素进行了研究。研究发现,农业技术和生产工具的进步、农村家庭收入来源中非农收入比例的提高、男孩较高的养育成本、社会保障的完善和人口流动性的增加所导致的人们对“养儿防老”预期的降低以及住房、交通条件的改善等一系列社会经济变化的共同作用,使人们的男孩偏好逐步淡化。     

出生性别比综合治理:有所为,有所不为

从1980年我国出生性别比越过正常值域至今,党和各级政府制订了种种措施进行综合治理,但取得的成效甚微。这一时期我国治理工作的特点有:重视禁止性法律法规的制定,但与之相配套的规章制度比较缺乏;重视目标任务的提出,但落实目标的措施比较缺乏;部门性、专项性规章制度较多,综合性规章制度比较缺乏。今后一段时期内综合治理工作,可以按照避实就虚、避难就易的原则,在大力发展社会经济、建立健全社会养老制度、相关法律法规的制定与完善、加大对两非行为的打击力度等方面有所作为;而在人口生育政策的调整、传统文化的改变等方面有所不为。     

台湾出生性别比的状况分析和对策研究

通过梳理有关台湾的人口资料,首先发现台湾出生性别比的发展呈现出总体偏高的趋势,其产生的原因是多种因素共同作用的结果。其次对台湾治理出生性别比偏高的直接和间接措施进行分析,直接措施是加大对非法性别鉴定的处罚,间接措施是消除不利文化的影响,营造促进妇女发展的社会环境。这些措施最终达到了＂标本兼治＂的目的。最后借鉴台湾治理出生性别比问题的经验和教训,为治理中国出生性别比偏高的问题提供相关对策。     

中国育龄妇女生育集中度变化分析——基于“五普”、“六普”数据

新中国成立以来,结束了上千年的封建制度给妇女带来的桎梏,妇女的社会地位有了明显的提升,具体表现在社会活动的参与率有了显著的提高,同时妇女在生育行为方面也发生了巨大的变化。本文利用最近两次中国人口普查数据来分析育龄妇女的生育集中度变化情况,并以此对中国目前TFR很低的现象做了解释,据此推断中国在未来几年的时间,总和生育率在一定程度上会呈上升的变化趋势,但不可能在短期内回升到更替水平。     

Frequency domain bootstrap for ratio statistics under long-range dependence

A frequency domain bootstrap (FDB) is a common technique to apply Efron’s independent and identically distributed resampling technique (Efron, 1979) to periodogram ordinates – especially normalized periodogram ordinates – by using spectral density estimates. The FDB method is applicable to several classes of statistics, such as estimators of the normalized spectral mean, the autocorrelation (but not autocovariance), the normalized spectral density function, and Whittle parameters. While this FDB method has been extensively studied with respect to short-range dependent time processes, there is a dearth of research on its use with long-range dependent time processes. Therefore, we propose an FDB methodology for ratio statistics under long-range dependence, using semi- and nonparametric spectral density estimates as a normalizing factor. It is shown that the FDB approximation allows for valid distribution estimation for a broad class of stationary, long-range (or short-range) dependent linear processes, without any stringent assumptions on the distribution of the underlying process. The results of a large simulation study show that the FDB approximation using a semi- or nonparametric spectral density estimator is often robust for various values of a long-memory parameter reflecting magnitude of dependence. We apply the proposed procedure to two data examples.     

‘Born this Way’? Prenatal exposure to testosterone may determine behavior in competition and conflict

Fetal exposure to sex hormones can have long lasting effects on human behavior. The second-to-fourth digit ratio (DR) is considered a putative marker for prenatal exposure to testosterone (vs estrogens), with higher exposure resulting in lower DR. Even though testosterone is theoretically related to competition, the role of DR in human behavior is debated; and in situations such as bilateral conflict is unknown. We investigate this through a laboratory experiment using a repeated 2-person Tullock contest played in fixed same-gender pairs. Based on a previously obtained large sample of student subjects, we selectively invited participants to the laboratory if their right-hand DR was in the top (High-DR) or bottom (Low-DR) tercile for their gender. Unbeknownst to the subjects, we performed a controlled match of the DR types (Low-Low, Low-High, High-High). This novel methodology allows us to analyze the causal effect of DR on behavior for the first time in the literature. We find that Low-DR (vs High-DR) males compete more aggressively regardless of the counterpart’s type. For females’ conflict behavior, the counterpart’s type matters more than the decision-maker’s type: Low-DRs are non-significantly more aggressive but every-one is more aggressive against High-DRs. Limitations due to sample size are discussed.