Production planning and inventories optimization: A backward approach in the convex storage cost case

We study the deterministic optimization problem of a profit-maximizing firm which plans its sales/production schedule. The firm controls both its production and sales rates and knows the revenue associated to a given level of sales, as well as its production and storage costs. The revenue and the production cost are assumed to be respectively concave and convex. In Chazal et al. [Chazal, M., Jouini, E., Tahraoui, R., 2003. Production planning and inventories optimization with a general storage cost function. Nonlinear Analysis 54, 1365–1395], we provide an existence result and derive some necessary conditions of optimality. Here, we further assume that the storage cost is convex. This allows us to relate the optimal planning problem to the study of a backward integro-differential equation, from which we obtain an explicit construction of the optimal plan.     

What divides the first and second generations? Family time of arrival and educational outcomes for immigrant youth

In this article, I develop a measure of host country experience, which I call “relative time of arrival,” to explore differences between first- and second-generation immigrants. This measure is finer than immigrant generation and expands on the widely used measures of years since migration and age at migration. It is scaled so that zero indicates that a child was born in the same year that the family migrated, and the negative side of the scale measures parents' host country experience before the child's birth. I then use relative time of arrival to assess whether parents' host country experience before birth matters and generally find that it does not. I also study the dividing line between the first and second generations, specifically, whether there are differences in educational outcomes between early arriving first-generation immigrants and second-generation immigrants whose parents arrived shortly before birth. For most outcomes considered, I find that the transition between the first and second generations is relatively smooth, indicating that these groups are not as distinct as often thought. Thus, observed differences between the first and second generations are driven by the lower performance of late-arriving first-generation children.     

GOVERNANCE INSTITUTIONS AND PRIVATE INVESTMENT: AN APPLICATION TO THE MIDDLE EAST AND NORTH AFRICA

This paper addresses the issue of the low level of private investment in the Middle East and North Africa (MENA) region, with special emphasis on the role of governance. Based on the existing published reports, we categorize what types of governance institutions are more detrimental to entrepreneurial investments. We then estimate a simultaneous model of private investment and governance quality where economic policies concurrently explain both variables. Our empirical results show that governance plays a significant role in private investment decisions. This result is particularly true in the case of “administrative quality” in the form of control of corruption, bureaucratic quality, investment‐friendly profile of administration, law and order, as well as for “political stability.” Evidence in favor of “public accountability” is also found. Our estimations also stress that structural reforms like financial development, trade openness, and human development affect private‐investment decisions directly, and/or through their positive effect on governance.     

Time to work or time to play: The effect of student employment on homework,sleep, and screen time

We use detailed time-diary information on high school students’ daily activities from the 2003–2008 American Time Use Surveys (ATUS) to investigate the effects of employment on the time a student spends on homework and other major activities. Time-diary data are more detailed and accurate than data derived from responses to “usual activity” survey questions underlying other analyses and capture the immediate effects of working that may well accumulate over time to affect future outcomes. Our results suggest that employment decreases the time that high school students spend on homework, which is human-capital building, on all days, but also decreases screen time on non-school days, which may be considered unproductive time. Employed teens get more than the recommended amount of sleep on school days, and only slightly less on non-school days.