Pivotal Statistics for Testing Structural Parameters in Instrumental Variables Regression

We propose a novel statistic for conducting joint tests on all the structural parameters in instrumental variables regression. The statistic is straightforward to compute and equals a quadratic form of the score of the concentrated log–likelihood. It therefore attains its minimal value equal to zero at the maximum likelihood estimator. The statistic has a χ² limiting distribution with a degrees of freedom parameter equal to the number of structural parameters. The limiting distribution does not depend on nuisance parameters. The statistic overcomes the deficiencies of the Anderson–Rubin statistic, whose limiting distribution has a degrees of freedom parameter equal to the number of instruments, and the likelihood based, Wald, likelihood ratio, and Lagrange multiplier statistics, whose limiting distributions depend on nuisance parameters. Size and power comparisons reveal that the statistic is a (asymptotic) size–corrected likelihood ratio statistic. We apply the statistic to the Angrist–Krueger (1991) data and find similar results as in Staiger and Stock (1997).     

农村贫困、收入不平等与城镇化关系的实证研究——基于2000—2012年省际面板数据

城镇化进程对经济和社会产生了巨大影响。通过计算中国省际层面2000—2012年城镇化率、农村贫困发生率和农村基尼系数,利用面板数据固定效应模型,研究中国农村贫困、农村不平等和城镇化的关系。研究发现:农村贫困发生率随着城镇化率提高而下降,城镇化率每提高1%,农村贫困发生率会降低2.87%;农村收入不平等随城镇化水平提高呈弱倒U型变化。同时,不同地区城镇化对农村贫困、农村收入不平等的影响也呈现不同趋势。在未来城镇化战略中,实施农村减贫政策时应兼顾调整收入分配政策,降低农村收入不平等。     

中美在南海问题上的外交博弈及其路径选择

中美围绕南海问题的较量类似"囚徒困境"博弈。由于利益冲突、缺乏互信以及联盟因素,中美在南海问题上的合作出现困境。如果上述问题得不到解决,该博弈就有可能转化为"谁是懦夫"博弈。南海问题的前景不容乐观。要解决中美南海博弈的外交困境,需要采取有效措施建立互信,并进行利益协调。     

上海女性弱势群体就业困境及其政策选择

在劳动就业日益个体化,劳动就业的稳定和保障逐渐消失的状况下,上海女性弱势群体的就业面临着内部资源缺乏与外部环境危机的多重困境。选择上海市女性弱势群体就业政策,不仅要促进上海市女性弱势群体的内部资源积累,还要创造上海市女性弱势群体就业的外部环境。     

Nonparametric Identification under Discrete Variation

This paper provides weak conditions under which there is nonparametric interval identification of local features of a structural function that depends on a discrete endogenous variable and is nonseparable in latent variates. The function delivers values of a discrete or continuous outcome and instruments may be discrete valued. Application of the analog principle leads to quantile regression based interval estimators of values and partial differences of structural functions. The results are used to investigate the nonparametric identifying power of the quarter‐of‐birth instruments used in Angrist and Krueger's 1991 study of the returns to schooling.     

“作为武器的弱者身份”：农民维权抗争的底层政治

社会弱者并不必然在任何时候都处于弱势地位,有时甚至拥有优势。在评述和借鉴农民维权抗争,特别是体现为“弱者的武器”的日常抵抗的相关研究的基础上,本文将农民底层政治的自主性作为分析农民的维权抗争的基点,同时将关注焦点放在农民维权抗争的日常事件上,从而发现了农民的另一种底层抗争的政治机制——“作为武器的弱者身份”。本研究论述了弱者所具有的隐性力量及以弱者身份作为武器进行抗争的作为,即回答了“作为武器的弱者身份”何以可能与何以可为的问题,从而对学界以往对弱者的传统认识提出了修正。本文最后指出,“作为武器的弱者身份”的抗争机制的研究对于社会管理与发展具有更深远的意义。     

当代农民道义→理性→抵抗的心理变化路径分析

20多年,“三农”发展印证了中国改革开放的每一个脚印。“三农”经济有了发展;农民有了实惠;农业有了提高;农村有了进步。商业化运动中土地资源凸现的价值使“三农”出现了新问题,即失地农民的利益被最终侵蚀时带来的农民心理变化或扭曲。     

“穷寇勿追”小考

从“穷寇”含义、早期有关的军事思想和具体战例等考察,“穷寇勿追”这一军事观念原初的正确表述形式应该是“穷寇勿迫”。“迫”之所以误作“追”,主要是由于汉代隶定后两字形近的缘故。     

有摩擦金融市场的弱无套利性

本文针对存在买进卖出差价和交易费两种摩擦形式的金融市场,利用凸分析、非线性规划等优化工具,给出了弱无套利的一个本质刻画,以及有关状态价格和弱无套利的一系列结果,推广了以往文献中的许多已知结果。     

Consistent Estimation with a Large Number of Weak Instruments

This paper analyzes the conditions under which consistent estimation can be achieved in instrumental variables (IV) regression when the available instruments are weak and the number of instruments, K_n, goes to infinity with the sample size. We show that consistent estimation depends importantly on the strength of the instruments as measured by r_n, the rate of growth of the so‐called concentration parameter, and also on K_n. In particular, when K_n→∞, the concentration parameter can grow, even if each individual instrument is only weakly correlated with the endogenous explanatory variables, and consistency of certain estimators can be established under weaker conditions than have previously been assumed in the literature. Hence, the use of many weak instruments may actually improve the performance of certain point estimators. More specifically, we find that the limited information maximum likelihood (LIML) estimator and the bias‐corrected two‐stage least squares (B2SLS) estimator are consistent when , while the two‐stage least squares (2SLS) estimator is consistent only if K_n/r_n→0 as n→∞. These consistency results suggest that LIML and B2SLS are more robust to instrument weakness than 2SLS.