Where Do Human Capital Externalities End Up To?

Recent literature has aimed at evaluating human capital externalities by estimating the effect of human capital on wages at urban level. We argue that this methodology might not identify properly human capital spillovers. We consider a general equilibrium model based on Roback (1982) where both wages and rents are simultaneously determined at the local level. We show that human capital externalities cannot be identified unless the joint effect of local human capital on both wages and rents is considered. Empirically, we study the effects of local human capital on household-level rents and individual-level wages for a sample of Italian local labor markets. Our results show a positive and robust effect of local human capital on rents. This unambiguously demonstrates that the concentration of human capital at the local level generates positive externalities. As for the relative importance of consumption and production externalities, our results suggest that the two effects have a similar impact on wages.

Where do human capital externalities end up?

Recent literature has aimed at evaluating human capital externalities by estimating the effect of human capital on wages at urban level. We argue that this methodology might not identify properly human capital spillovers. We consider a general equilibrium model based on Roback (1982) where both wages and rents are simultaneously determined at the local level. We show that human capital externalities cannot be identified unless the joint effect of local human capital on both wages and rents is considered. Empirically, we study the effects of local human capital on household-level rents and individual-level wages for a sample of Italian local labour markets. Our results show a positive and robust effect of local human capital on rents. This unambiguously demonstrates that the concentration of human capital at the local level generates positive externalities. As for the relative importance of consumption and production externalities, our results suggest that the two effects have a similar impact on wages.human capital; externalities; local markets

Resources and Incentives to Reform

This paper models the incentives for a self-interested government to implement "good policies." While good policies lead to investment and growth, they also reduce the government's ability to reward its supporters. The model predicts that resource abundance leads to poor policies and, consequently, to low investment. The implications of the model are broadly supported by existing evidence. In particular, countries that are rich in natural resources tend to have low institutional quality and poor macroeconomic and trade policies. Copyright 2003, International Monetary Fund

Skill-Biased Share-Altering Technical Change in Spatial General Equilibrium

The paper consider the skill-biased “share-altering†technical change hypothesis in a spatial general equilibrium model where skilled and unskilled individual may exhibit different preferences for local amenities. A main novelty –both for labour and urban economics- is that, under this hypothesis, skill-biased technical change can be readily represented by simple Cobb-Douglas production functions, rather than CES technologies. We then analyse the local labour markets equilibrium, where the adoption of new technologies may require an adequate proportion of skilled workers. Keywords: skill-biased technical change, share-altering technologies, local labour markets. JEL Classification Numbers: O33, R12, R23, J31.

Skill Polarization in Local Labour Markets under Share-Altering Technical Change

This paper considers the “share-altering” technical change hypothesis in a spatial general equilibrium model where individuals have different levels of skills. Building on a simple Cobb-Douglas production function, our model shows that the implementation of skill-biased technologies requires a sufficient proportion of highly educated individuals. Moreover, areas that experiment this kind of technical change will initially exhibit a rise in local skill premia, but such a trend tends to be reverted over time due to labour mobility. Also, when technical progress is such to disproportionately replace middle-skill jobs, the local distribution of skill will exhibit “fat-tails”, where the proportion of both highly skilled and low-skilled workers increases. These predictions are consistent with recent existing evidence.share-altering technologies, local skill distribution, local wage premium.

Diversity and biological aspects of wild bees in an urban and a natural environment in the central region of Santa Fe, Argentina

El objetivo del presente trabajo fue relevar el elenco de abejas silvestres en la región central de Santa Fe y comparar la diversidad de especies y aspectos biológicos en dos ambientes de una misma región. Las abejas fueron colectadas en el estrato herbáceo de la Reserva Universitaria “Escuela Granja” de la localidad Esperanza, y en la zona urbana de la localidad Susana, ambas ubicadas dentro de la Provincia Fitogeográfica del Espinal. La colecta se realizó en octubre, noviembre y diciembre de 2004 y en enero, febrero y marzo de 2005, registrando las especies vegetales sobre las que se capturaron. Se colectaron 277 ejemplares en total, de los cuales se identificaron 62 especies (27 géneros en 5 familias). Las curvas de rarefacción indican una tasa de acumulación de especies mayor para la Reserva Ecológica, los índices de diversidad de Shannon son 3,25 para la Reserva Ecológica y 2,64 para la Zona Urbana. Para la comparación de las comunidades en ambos sitios, las abejas fueron clasificadas en tres categorías según la especialización en el uso del recurso floral, sustrato de nidificación y comportamiento social. Se observó una asociación entre los grupos especialistas y de nidificación en el suelo con el ambiente natural, y por otro lado, las especies generalistas y de nidificación en cavidades con el ambiente urbano. No se identificaron diferencias, en cuanto al tipo de comportamiento social de las especies, entre ambos sitios.The purpose of this contribution is to present a survey of wild bees in the central region of Santa Fe, and to compare the diversity and biological aspects of the bee communities at two different environments of the same region. Bees were surveyed at the ecological reserve Reserva Universitaria “Escuela Granja” in the locality of Esperanza, and at an urban area in the locality of Susana, both in the Espinal Phytogeographic Province. Bees were sampled from October to December 2004 and from January to March 2005, recording their plant associations. A total of 277 specimens were collected, belonging to 62 species (27 genera in 5 families). The rarefaction curves indicate a higher rate of species accumulation for the ecological reserve; the Shannon diversity index was 3.25 for the ecological reserve and 2.64 for the urban area. In order to compare the composition of the bee communities at the two sites, the bees were classified into three categories: degree of specialization in the use of floral resources, nesting substrate, and social behavior. It was observed that specialized bees who nest in the soil showed an association with the natural environment while the generalist species who nest in pre-existing cavities showed an association with the urban environment. No association was found between type of social behavior and type of environment.Fil: Dalmazzo, Maria de Los Milagros. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentin

Deformation Behavior of Clay-Water Suspensions

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Rutting Behaviour of Wearing Course Mixtures in Severe Temperature and Loading Conditions

Following the construction of a major motorway pavement in Northern Africa, relevant rutting phenomena were observed after opening to traffic. Preliminary investigations showed that permanent deformations were limited to the upper wearing course layer which was designed according to set requirements. In order to define the most appropriate rehabilitation strategy, investigations were carried out by focusing on the volumetric and mechanical properties of the employed wearing course mixture. Compaction properties were assessed by making use of a gyratory shear compactor and of a rubber-wheeled roller. Moreover, simulative wheel-tracking tests were carried out in severe temperature and loading conditions. Additional tests were performed on an alternative bituminous mixture containing polymer granules. Based on the obtained results the possible causes of the above described distress phenomena were identified and the use of the alternative bituminous mixture as a technical solution to adopt for rehabilitation was considere

Fatigue Characterization of Bituminous Binders Containing Crumb Rubber from End-of-Life Tires

This paper presents the outcomes of an experimental investigation which focused on the fatigue behavior of bituminous binder for paving applications prepared by combining a single reference neat bitumen with different types of crumb rubber products derived from the processing of end-of-life tires. In the laboratory preparation of the blends, crumb rubber dosage was conveniently limited in order to obtain binders characterized by viscosity values compatible with standard operating conditions normally adopted in the production and compaction of bituminous mixtures. Results obtained from time sweep tests carried out in equi-stiffness conditions showed that fatigue performance is enhanced by the use of the considered crumb rubber modifiers with a dosage-dependent improvement of both fatigue life and crack propagation amplitude. Given that the considered crumb rubber products were quite similar, no significant effects were associated to changes of crumb rubber type