Risk aversion, intertemporal substitution, and the aggregate investment-uncertainty relationship

We analyze the role of risk aversion and intertemporal substitution in a simple dynamic general equilibrium model of investment and savings. Our main finding is that risk aversion cannot by itself explain a negative relationship between aggregate investment and aggregate uncertainty, as the effect of increased uncertainty on investment also depends on the intertemporal elasticity of substitution. In particular, the relationship between aggregate investment and aggregate uncertainty is positive even if agents are very risk averse, as long as the elasticity of intertemporal substitution is low. A negative investment-uncertainty relationship requires that the relative risk aversion and the elasticity of intertemporal substitution are both relatively high or both relatively low. We also show that the implications of our model are consistent with the available empirical evidence

Wild Plant Genetic Resources in North America: An Overview

North America, including Canada, Mexico, and the United States, is rich in plant species used by humans in both ancient and modern times. A select number of these have become globally important domesticated crops, including maize, beans, cotton, and sunflower. Many other native and also naturalized species have potential for use, either directly or as genetic resources for breeding agricultural crops. However, despite increasing recognition of their potential value, deficiencies in information, conservation, and access to the diversity in these plants hinder their further use. This chapter provides an overview of the agriculturally relevant wild plant resources of North America, with focus on wild relatives of globally important major crops, as well as the wild cousins of regionally and locally important domesticates. The chapter concludes by providing an overview of strategies for conserving wild plant genetic resources, including the international regulatory frameworks affecting policies to various degrees in Canada, Mexico, and the United States

Fostering spatial ability development in and for authentic STEM learning

Empirical interdisciplinary research has explored the role of spatial ability in STEM learning and achievement. While most of this research indicates that fostering spatial thinking in educational contexts has the potential to positively impact students’ enrollment and performance in STEM subjects, there is less agreement on the best approach to do so. This article provides an overview of various types of effective spatial interventions and practices in formal or informal educational contexts, including targeted training of STEM-relevant spatial skills, spatialized curricula embedded in schools, integrated STEM practices addressing students’ use of spatial skills, and spatial activities in informal STEM education. Gender and socio-economic status of students – two variables that have been found to moderate the relationship between students’ spatial ability and their STEM performance – are also discussed in this article. Drawing on a wide spectrum of perspectives on situating spatial ability research in STEM education contexts, this article underscores the need for further inquiry into opportunities for developing K-12 students’ spatial ability through integrated and informal STEM practices. This article proposes a conjecture that the relationship between developing students’ spatial ability and enhancing their abilities to solve spatially complex STEM problems is bidirectional. Recommendations for future research are made on lingering questions about the effect of interventions, untapped resources for spatial ability training in formal and informal STEM education, and educational strategies for developing students’ spatial ability in authentic learning environments.</p

Dinâmica do emprego e custos de ajustamento na indústria do Rio Grande do Sul

O presente estudo tem como propósito fazer uma análise empírica da estrutura dos custos de ajustamento do emprego industrial usando dados do Brasil. As estruturas teóricas para custos de ajustamento do emprego encontradas na literatura podem ser agrupadas em custos convexos (que incluem a popular função quadrática) e não-convexos (como custos fixos). Seguindo o trabalho de Varejão e Portugal (2007), empregamos metodologias complementares para a identificação da estrutura de custos de ajustamento de modo inovador no Brasil. Primeiro, usando matrizes de transição entre regimes de emprego. Segundo, empregando modelos de sobrevivência, que são mais gerais que os modelos de matriz de transição Markoviana. Os resultados obtidos sugerem que os custos de ajustamento não-convexos têm mais apoio nos dados do que o modelo usual de custos de ajustamentos quadráticos.<br>We evaluate the structure of adjustment costs in manufacturing employment using Brazilian firm data. While quadratic adjustment costs are widely used this type of costs are not compatible with the extensive within sector gross job flows. Following Varejão and Portugal (2007), we use survival analysis as an empirical tool, as previous results associate non-convex adjustment costs with inactivity time dependent exit probabilities. Our estimates using quarterly firm level data from manufacturing industries, from 1991 to 2004 soundly reject time independent exit probabilities from labor adjustment inactivity, a result that is compatible with non-convex adjustment costs