出口企业转型与企业的经营表现

 文章运用基于倍差法的倾向评分匹配估计方法从企业微观层面分析了出口企业转型对其经营表现的作用。结果表明：高度外销型企业转型为中度外销型企业以及中度外销型企业转型为低度外销型企业对企业经营表现的影响主要体现于其会显著地增加企业的负债额进而恶化其财务状况，二者不显著影响企业的劳动生产率和产出。高度外销型企业转型为低度外销型企业对企业经营表现的影响主要体现于其会显著地提高企业的劳动生产率，这种转型行为并不显著影响企业的产出和财务状况。尽管如此，由于其对企业的产出并不产生显著作用，因此由于该转型行为所获得的劳动生产率的提升同时也会减少企业的就业。     

A comparison of species diversity estimators

Although having been much criticized, diversity indices are still widely used in animal and plant ecology to evaluate, survey, and conserve ecosystems. It is possible to quantify biodiversity by using estimators for which statistical characteristics and performance are, as yet, poorly defined. In the present study, four of the most frequently used diversity indices were compared: the Shannon index, the Simpson index, the Camargo eveness index, and the Pielou regularity index. Comparisons were performed by simulating the Zipf–Mandelbrot parametric model and estimating three statistics of these indices, i.e., the relative bias, the coefficient of variation, and the relative root-mean-squared error. Analysis of variance was used to determine which of the factors contributed most to the observed variation in the four diversity estimators: abundance distribution model or sample size. The results have revealed that the Camargo eveness index tends to demonstrate a high bias and a large relative root-mean-squared error whereas the Simpson index is least biased and the Shannon index shows a smaller relative root-mean-squared error, regardless of the abundance distribution model used and even when sample size is small. Shannon and Pielou estimators are sensitive to changes in species abundance pattern and present a nonnegligible bias for small sample sizes (<1000 individuals). Received: May 8, 1998 / Accepted: May 6, 1999     

An algorithm to determine the parameters of SU -curves in the johnson system of probabillity distributions by moment matching ∗

We describe an algorithm to fit an S_U -Curve of the Johnson system by moment matching. The algorithm follows from a new parametrization, and reduces the problem to a root finding procedure that can be implemented efficiently using a bisection or a Newton-Raphson method. This allows the four parameters of the Johnson curve to be determined to any desired degree of accuracy, and is fast enough to be implemented in a real-time setting. A practical application of the method lies in the fact that many firms use the Johnson system to manage financial risk     

Autocorrelation and tolerance limits

Tolerance limits are limits that include a specified proportion of the population at a given confidence level. They are used to make sure that the production will not be outside specifications. Tolerance limits are either designed based on the normality assumption, or nonparametric tolerance limits are established. In either case, no provision for autocorrelated processes is made in the available design tables of tolerance limits. It is shown how to construct tolerance limits to cover a specified proportion of the population when autocorrelation is present in the process. A comparison of four different tolerance limits is provided, and recommendations are given for choosing the "best" estimator of the process variability for the construction of tolerance limits.     

劳动力市场匹配效率的影响因素研究

当前就业难、用工荒并存的重要原因是劳动力市场不健全导致匹配效率低。本文基于面板数据,利用自适应Lasso方法对我国劳动力市场匹配效率的影响因素进行实证研究。研究发现,技工学校等职业培训机构、人才市场等职业市场机构的发展对劳动力市场匹配效率有显著影响,相对于需求方而言,提高匹配效率应更多从供给侧入手,这是根本之策。应整合优化职业教育资源,提高劳动力质量和适用性,更好地满足加快建设创新型国家、全面建设现代化经济体系的需要。     

Bounds on the empirical Bayes and compound risks of truncated versions of Robbins's estimator of a binomial parameter

Robbins (1956) in his original paper on empirical Bayes methods suggested a method of estimating a binomial success probability. We give explicit bounds for the empirical Bayes risk of natural variants of the Robbins estimator that show convergence to an optimal risk at $\text{O(n}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{)}$ rate. Bounds that yield the same convergence rate are also obtained in the related compound estimation problem.     

自我雇佣的收入效应、发展特征及其群体差异

自我雇佣兼具增加就业和提高收入的功能。运用倾向得分匹配法,使用2002年和2013年CHIP数据,估算了我国自我雇佣就业的收入效应。研究发现:(1)我国自我雇佣整体上呈现收入溢价效应;(2)2013年自我雇佣者的收入溢价效应明显高于2002年;(3)城镇自我雇佣劳动者获得的收入溢价不仅在绝对值上高于农民工自我雇佣者,而且在增长幅度上也大于后者;(4)作为成功的自我雇佣者,雇主获得的收入溢价大大高于非雇主;(5)受教育水平、经营起始资金数量是决定自我雇佣者能否成功的关键。据此,采取各项措施帮助有创业意愿的劳动者实现自我雇佣,尤其是加大自我雇佣者的人力资本培训力度和创业资金支持力度,助力他们成长为成功的自我雇佣者,既有利于提高我国劳动者的收入水平,也有利于实现我国提高就业质量的政策目标。     

On Ring Grooming in optical networks

An instance I of Ring Grooming consists of m sets A ₁,A ₂,…, A _m from the universe {0, 1,…, n − 1} and an integer g ≥ 2. The unrestricted variant of Ring Grooming, referred to as Unrestricted Ring Grooming, seeks a partition {P ₁ , P ₂, …,P _k } of {1, 2, …, m} such that for each 1 ≤ i ≤ k and is minimized. The restricted variant of Ring Grooming, referred to as Restricted Ring Grooming, seeks a partition of {1,2,…,m} such that | P _i | ≤ g for each and is minimized. If g = 2, we provide an optimal polynomial-time algorithm for both variants. If g > 2, we prove that both both variants are NP-hard even with fixed g. When g is a power of two, we propose an approximation algorithm called iterative matching. Its approximation ratio is exactly 1.5 when g = 4, at most 2.5 when g = 8, and at most in general while it is conjectured to be at most . The iterative matching algorithm is also extended for Unrestricted Ring Grooming with arbitrary g, and a loose upper bound on its approximation ratio is . In addition, set-cover based approximation algorithms have been proposed for both Unrestricted Ring Grooming and Restricted Ring Grooming. They have approximation ratios of at most 1 + log g, but running time in polynomial of m ^g . Work supported by a DIMACS postdoctoral fellowship.     

Random Matching Under Dichotomous Preferences

We consider bilateral matching problems where each person views those on the other side of the market as either acceptable or unacceptable: an acceptable mate is preferred to remaining single, and the latter to an unacceptable mate; all acceptable mates are welfare‐wise identical. Using randomization, many efficient and fair matching methods define strategyproof revelation mechanisms. Randomly selecting a priority ordering of the participants is a simple example. Equalizing as much as possible the probability of getting an acceptable mate across all participants stands out for its normative and incentives properties: the profile of probabilities is Lorenz dominant, and the revelation mechanism is groupstrategyproof for each side of the market.