非对称信息市场理论对规范中国劳动力市场秩序的启示

信息不对称是导致中国劳动力市场秩序混乱的主要原因之一。斯宾塞的劳动力市场模型解决了信息非对称条件下的均衡实现问题,同时也揭示了信息不对称下均衡效率低下、劳动力市场混乱的事实。运用这一模型对我国劳动力市场存在的问题作了进一步解释,并提出了规范我国劳动力市场的对策。     

Split Hamiltonian Monte Carlo

We show how the Hamiltonian Monte Carlo algorithm can sometimes be speeded up by “splitting” the Hamiltonian in a way that allows much of the movement around the state space to be done at low computational cost. One context where this is possible is when the log density of the distribution of interest (the potential energy function) can be written as the log of a Gaussian density, which is a quadratic function, plus a slowly-varying function. Hamiltonian dynamics for quadratic energy functions can be analytically solved. With the splitting technique, only the slowly-varying part of the energy needs to be handled numerically, and this can be done with a larger stepsize (and hence fewer steps) than would be necessary with a direct simulation of the dynamics. Another context where splitting helps is when the most important terms of the potential energy function and its gradient can be evaluated quickly, with only a slowly-varying part requiring costly computations. With splitting, the quick portion can be handled with a small stepsize, while the costly portion uses a larger stepsize. We show that both of these splitting approaches can reduce the computational cost of sampling from the posterior distribution for a logistic regression model, using either a Gaussian approximation centered on the posterior mode, or a Hamiltonian split into a term that depends on only a small number of critical cases, and another term that involves the larger number of cases whose influence on the posterior distribution is small.     

The Detection of Influential Observations for Allocation,Separation, and the Determination of Probabilities in a Bayesian Framework

Normal theory separation and allocation problems are discussed from a predictive point of view. Influence statistics are defined and employed to ascertain the impact that particular observations will have on the inferential goals—allocation of future observations, separation between populations, and the determination of probabilities for future cases. Methods are illustrated on a collection of financial data taken from Johnson and Wichern (1982).     

Does the capital of social capital matter? Relational resources of the board and the performance of Brazilian companies

Based on theories of social capital, in this study, we seek to assess the impact of a board’s social capital on the market value of companies listed on the Brazilian stock exchange. As our indicator of social capital, we use the relational resources identified in the direct, indirect and heterogeneous ties of the board. Employing panel data from 508 observations, our results indicate that heterogeneous relational resources have a stronger and more significant influence than the resources available from board members’ direct relationships. Additionally, as the effects of board interlock are endogenously determined by several factors related to the firm level, we seek to mitigate the endogeneity problem using models of instrumental variables and simultaneous equations. Our hypotheses were consistent after controlling for endogeneity. We also check whether the board’s social capital could present a U-inverted effect on the market value. This relationship was only plausible in social capital by indirect ties. Finally, we isolate the effect of relational resources within and between industries on Tobin’s Q. There was no significant effect through interlocks within the same industry. However, ties with companies in several other industries were significant.     

Government Capital,Intimate and Community Social Capital,and Food Security Status in Older Adults with Different Income Levels

Whether government‐based forms of food assistance such as the Supplemental Nutrition Assistance Program (SNAP), communal efforts including food pantries, aid from friends and family, or alternative means such as gardening are the appropriate means to reduce the prevalence of household food insecurity is a continuous source of policy contention. To inform this debate, we examine the relative importance of these forms of food assistance and acquisition to a sample of U.S. older adults from the 2010 Brazos Valley Health Assessment of central Texas households that have been stratified by income eligibility for SNAP, low‐income SNAP ineligibility, and above low income status. To identify how membership in these socioeconomic groups constrains household capacity to acquire sufficient food to maintain an adequate and healthy diet, we explore the varied associations of assets received from government; communal and intimate social networks; and alternative food sources such as gardening, hunting, and fishing with household food security across socioeconomic status, while examining the importance of place of residence on the use of capital assets. SNAP participation was the only specific capital asset associated with all levels of food insecurity for both SNAP‐eligible and ineligible low‐income groups, thus emphasizing the continued importance of food assistance among poverty‐level older adults.     

Physical variation in low-load work - physiological effects during exposure & recovery

Trends in industry are leaning towards jobs that are more stereotyped at lower workloads. Physical variation is a potential ergonomic intervention. However, little is known of physiological response to different kinds of variation. To investigate this issue, three kinds of isometric contraction patterns with the same mean amplitude, cycle time, and duty cycle were compared. Fatigue responses were measured by multiple biomechanical and physiological approaches. In exercise, sustained and intermittent contractions with zero force had a greater number of statistically significant differences in fatigue responses. Intermittent contractions with amplitude ? and 1? of mean force had effects intermediate but close to the sustained contraction. In recovery, sustained contractions led to decreased twitch forces 24 hours post-exercise whereas both intermittent contractions recovered within 60 minutes. This suggests that time varying forces, even without complete muscular rest, may be a useful intervention to reduce local and perceived fatigue in workers performing low-load tasks.     

The Effect of 21st Century Military Service on Civilian Labor and Educational Outcomes

I estimate the effect of military service during the Afghanistan and Iraq wars on civilian labor and educational outcomes using several empirical methodologies including sibling fixed effects and propensity score matching. Since military occupations and training have changed significantly in the past few decades, these effects may be different than those found in previous studies on veterans of earlier theaters. I find that veteran status increases civilian wages by approximately ten percent for minorities but has little or no effect on whites in this regard. Veterans of all demographic groups are found to be equally employable and equally as satisfied with their civilian occupation as non-veterans. For females and minorities, veteran status substantially increases the likelihood one attempts college. These veterans are found to be more apt to pursue and obtain a two year (associate’s) degree instead of a four year (bachelor’s) degree. Lastly, I find mixed evidence that veteran status increases the likelihood of public sector employment.     

The Probability of Teenage Parenthood: Parental Predictions and Their Accuracy

Teenage parenthood is an often-discussed topic in family economics since it has been shown to affect many outcomes for the teen, child, and household. Using a nationally representative longitudinal panel of American teenagers and their parents, two questions related to the probability of teenage parenthood are examined. First, how do predictions of this occurrence made by the teenager’s parents vary across the population? Second, how does the accuracy of these predictions vary? The actual prevalence and variance of teenage parenthood are also examined, and the determinants of its occurrence are estimated. Among other results, expectations and their accuracy are found to differ substantially across socioeconomic status and some demographics such as race and religion. The average American parent underestimates the probability their child will become a teen parent by only a small amount, but within certain demographic groups this outcome is considerably underestimated, and in others it is overestimated. These differences help explain the variability in teen parenthood effects, and more broadly, the analysis serves as a test of parents’ ability to judge their childrens’ future outcomes.     

An evaluation of physical fitness parameters for graduate students

Although graduate physical therapy students are taught the principles of fitness for incorporation into their professional lives, they have difficulty finding the time to implement these principles during graduate school. The authors studied 3 successive classes of graduate physical therapy students at the beginning and ending of their respective programs. They found that the women's percentages of body fat were significantly greater over the period of the study. The men's lower extremity strength decreased at the slower speeds (60 degrees/second), and the women showed increased strength at the higher speeds (180 and 240 degrees/second, respectively). Male grip strength significantly increased over the period of the study. To decrease students' percentages of body fat and increase their strength, the authors asserted that physical therapy students should be allowed more time to participate in fitness activities during their graduate school years.