Inefficient Job Destructions and Training with Hold‐up

This paper develops an equilibrium search model with endogenous job destructions and where firms decide at the time of job entry how much to invest in match‐specific human capital. We first show that job destruction and training investment decisions are strongly complementary. It is possible that there are no firings at equilibrium. Further, training investments are confronted to a hold‐up problem making the decentralized equilibrium always inefficient. We show therefore that both training subsidies and firing taxes must be implemented to bring back efficiency.     

SNA关于资本服务的测算及对国民账户的影响

 资本服务测算是资本测算中的重要内容。最新修订的2008年SNA首次引入资本服务的概念,在肯定资本服务对生产率测算和其他分析的重要意义后,新增了一章来阐述资本服务的功能和表现。本文主要介绍资本服务的基本概念、资本服务与相关概念的辨析、资本服务的测算方法,并分析引入资本服务对国民账户可能带来的影响。     

Policy convergence under approval and plurality voting: the role of policy commitment

Proponents of Approval Voting argue that this electoral rule leads to more centrist outcomes compared to Plurality Voting. This claim has been substantiated by scholarly work using spatial models of political competition. We revisit this issue in the context of a model of political competition in which (1) candidates are policy-motivated; (2) candidacy decisions are endogenous; and (3) candidates can credibly commit to implementing any policy. Under these assumptions we find the opposite to be true – Plurality Voting yields convergence to the median voter’s ideal policy but Approval Voting may not. We argue that this result is driven by the differential incentives for candidate entry under the two voting rules. Our results suggest that whether Approval Voting yields more centrist outcomes vis-á-vis Plurality Voting depends on the possibility of policy commitment on the part of the candidates. In an election held under PV each citizen is given one vote he can cast for one (and only one) candidate, and the candidate who gets the most votes wins the election.     

On inspecting multiparameter likelihood surfaces

A computer-based graphical method for comparing a multi parameter log likelihood surface with its quadratic approximation is presented. The method can be used to visualize certain aspects of any highdimensional surface near a local maximum, Examples are given to illustrate the interpretation and use of the resulting plots.     

Distributions and moments of record values in a sequence of maximally dependent random variables

A sequence of possibly dependent random variables is maximally dependent if all the sample maxima in the sequence have stochastically maximal distributions in the class of all distributions with the same marginals. For a sequence of maximally dependent standard uniform random variables, we determine the distribution functions of record times and values. We show that the distribution of the record occurrence times coincides with the respective distribution for the i.i.d. sequence, and the distributions of the record values are stochastically maximal in the class of sequences with the same record times distributions, containing all the exchangeable sequences. We also derive analytic formulae for the moments of record values from the maximally dependent sequence, and compare them with those of the i.i.d. case.     

Effects of Tai Chi exercises on self-efficacy and psychological health

This review offers an update of the psychological effects of Tai Chi Chuan (TC) among different populations. A computerized literature research from 1990 to June 2006 was carried out. Studies were selected when they assessed the mental and psychological effects of TC practice among various populations. Data from 14 studies for a total of 829 subjects, age range from 12 to 96 years, were considered here. There were eight randomized controlled trials and six quasi-experimental or case control studies in this review. The intensity of TC varied from 30 min twice a week over a 5-week period to 1 h every day over an 8-week period. TC was characterized as a kind of light-to-moderate exercise and was found to enhance overall psychological well-being and to improve self-efficacy and mood. TC benefits appeared to be more tangible for adults and healthy older adults or those becoming frail. However, TC did not appear to be more efficient than exercises of the same intensity. Extensive and qualitative studies are needed to quantify the effects of the volume of practice, expert modeling, gender differences, and the age-related learning process on efficacy cognitions and mood in clinical and nonclinical contexts.     

Distribution of record statistics in a geometrically increasing population

The probability function and binomial moments of the number _Nn$N_n$ of (upper) records up to time (index) n in a geometrically increasing population are obtained in terms of the signless q-Stirling numbers of the first kind, with q   being the inverse of the proportion λ$\lambda$ of the geometric progression. Further, a strong law of large numbers and a central limit theorem for the sequence of random variables _Nn$N_n$, n=1,2,…,$n=1,2,\dots ,$ are deduced. As a corollary the probability function of the time _Tk$T_k$ of the kth record is also expressed in terms of the signless q  -Stirling numbers of the first kind. The mean of _Tk$T_k$ is obtained as a q  -series with terms of alternating sign. Finally, the probability function of the inter-record time _Wk=_Tk-_Tk-1$W_k=T_k-T_{k-1}$ is obtained as a sum of a finite number of terms of q  -numbers. The mean of _Wk$W_k$ is expressed by a q-series. As k   increases to infinity the distribution of _Wk$W_k$ converges to a geometric distribution with failure probability q. Additional properties of the q-Stirling numbers of the first kind, which facilitate the present study, are derived.     

Are the <Emphasis Type="Italic">Generations and Gender Surveys</Emphasis> Well Suited for Studying Same-Sex Couples?

Different studies of same-sex couples based on the Generations and Gender Survey (GSS) have been published in recent years. However, in this survey, people in gay and lesbian couples are not identified via a direct question but by comparing two separate variables: the sex of the respondent and that of the partner. But the identification of same-sex couples by comparing the sex of both partners is very unreliable. The few sex-coding errors of one of the partners in heterosexual couples generate a very high proportion of “false” same-sex couples among all couples considered to be of the same sex. The aim of this paper is to demonstrate the problematic nature of the indicator in order to avoid inappropriate use of GGS data (and other surveys more generally) and to discuss the reliability of analyses of same-sex couples made with these data.     

Asymptotic approximation of the likelihood of stationary determinantal point processes

Continuous determinantal point processes (DPPs) are a class of repulsive point processes on ${ℝ}^d$ with many statistical applications. Although an explicit expression of their density is known, it is too complicated to be used directly for maximum likelihood estimation. In the stationary case, an approximation using Fourier series has been suggested, but it is limited to rectangular observation windows and no theoretical results support it. In this contribution, we investigate a different way to approximate the likelihood by looking at its asymptotic behavior when the observation window grows toward ${ℝ}^d$. This new approximation is not limited to rectangular windows, is faster to compute than the previous one, does not require any tuning parameter, and some theoretical justifications are provided. It moreover provides an explicit formula for estimating the asymptotic variance of the associated estimator. The performances are assessed in a simulation study on standard parametric models on ${ℝ}^d$ and compare favorably to common alternative estimation methods for continuous DPPs.