Immigration accounting: U.S. states 1960-2006

Different U.S. states have been affected by immigration to very different extents in recent years. Immigration increases available workers in a state economy and, because of its composition across education groups, it also increases the relative supply of less educated workers. However, immigration is more than a simple labor supply shock. It brings differentiated skills and more competition to the labor market and it may induce efficient specialization and affect the choice of techniques. Immigrants also affect investments, capital accumulation, and the productivity of more and less educated workers. Using a production function-based procedure and data on gross state product, physical capital and hours worked we analyze the impact of immigration on production factors (capital, more and less educated labor), and productivity over the period 1960-2006 for 50 U.S. states plus D.C. We apply growth accounting techniques to the panel of states in order to identify the changes in factors and productivity associated with immigration. To identify a causal impact we use the part of immigration that is determined by supply shifts in countries of origin and the geographical location of U.S. states or historical immigrants’ settlements. We find that immigration significantly increased the relative supply of less educated workers, that it did not affect much the level of capital per worker and that it significantly increased the productivity of highly educated workers and, even more, less educated workers. These channels together explain the small effect of immigrants on wages of less educated workers and the significant positive effects on wages of more educated workers

A randomized clinical trial about presence of pathogenic microflora and risk of peri-implantitis: comparison of two different types of implant-abutment connections

OBJECTIVE: The aim of this in vivo study was to evaluate two different types of implant-abutment connections: screwed connection and cemented connection, analyzing peri-implant bacteria microflora as well as other clinical parameters. PATIENTS AND METHODS: Twenty implants were selected, inserted in 20 patients, 10 with a screwed implant-abutment connection (Group 1) and 10 with a cemented implant-abutment connection (Group 2). The peri-implant microflora was collected, after at least 360 days from the prosthetic rehabilitation, using paper points inserted in peri-implant sulcus for 30 s. Polymerase chain reaction (PCR) Real-time analyzed the presence of 9 bacteria periodontal-pathogens and Candida albicans. RESULTS: Our findings showed that bacteria colonized all Groups analyzed, the average bacterial count was 3.7 E +08 (±1.19) in Group 1, compared to 2.1 E +08 (±0.16) in Group 2; no statistically significant differences were observed (p>0.0.5). In Group 1, however, bacterial colonization of peri-implant sulci was over the pathogenic threshold for 5 bacteria, indicating a high-risk of peri-implantitis. Also in Group 2, results showed a microflora composed by all bacteria analyzed but, in this case, bacterial colonization of peri-implant sulci was over the pathogenic threshold for only 1 bacterium, indicating a lower risk of peri-implantitis. Moreover, clinical parameters (PPD > 3 mm and m SBI > 0) confirmed a greater risk of peri-implantitis in Group 1 compared to Group 2 (p<0.05). CONCLUSIONS: We concluded that, also after only 360 days, implants with screwed connection showed a higher risk of peri-implantitis that implants with cemented connection

A Novice's Process of Object-Oriented Programming

Exposing students to the process of programming is merely implied but not explicitly addressed in texts on programming which appear to deal with 'program' as a noun rather than as a verb.We present a set of principles and techniques as well as an informal but systematic process of decomposing a programming problem. Two examples are used to demonstrate the application of process and techniques.The process is a carefully down-scaled version of a full and rich software engineering process particularly suited for novices learning object-oriented programming. In using it, we hope to achieve two things: to help novice programmers learn faster and better while at the same time laying the foundation for a more thorough treatment of the aspects of software engineering

Landscape heterogeneity influences on sheep habits under extensive grazing management in Southern Patagonia

In Southern Patagonia, continuous grazing with fixed stocking rates in large paddocks prevails over grazing systems subjected to regular evaluations and rotational rests. Because of this, sheep extensive systems need technologies to improve their production levels under sustainable management. In this context, the aim of this work was to provide knowledge of sheep habits (diet, daily activity and spatial distribution patterns) in seven paddocks at a production scale throughout the year in Southern Patagonia. The area is an extensive ecotone between forest and steppe, characterized by a rugged landscape with valleys and mountains. Three vegetation types were distinguished in each paddock: forest, steppe and wetland. After a two years trial, sheep showed an important array of strategies for facing restrictions imposed by climate and low forage availability. A strong dietary selectivity, a high percentage of time allocated to grazing, large explored areas and opportunistic selection of vegetation types explained the capacity for reproduction under Southern Patagonia harsh conditions. The application of an intensified management involving paddock subdivision and separation of vegetation types should consider how sheep grazing strategies are limited.Fil: Peri, Pablo Luis. Instituto Nacional de Tecnología Agropecuaria; Argentina. Universidad Nacional de la Patagonia Austral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

METROPOLITAN AGRICULTURE, SOCIO-DEMOGRAPHIC DYNAMICS AND THE FOOD-CITY RELATIONSHIP IN SOUTHERN EUROPE

Peri-urban agriculture is a pivotal issue in the debate on sustainable management of land in metropolitan regions worldwide. Multiple socioeconomic and environmental solutions introduced by new models of peri-urban agriculture are playing an important role in planning and management of fringe land. The recent development of peri-urban agriculture in Southern European cities was supposed to reflect latent, crisis-driven processes of 'coming back to land': new land has been extensively cultivated, and new relations have been created between farmers, communities and territories within peri-urban areas. This study describes some relevant experiences of peri-urban farming in 6 metropolitan regions (Lisbon, Barcelona, Marseille, Rome, Athens, Istanbul) representative of different socioeconomic contexts in Southern Europe, outlining strengths and weaknesses in the use of fringe land for cropping, and evidencing relevant implications for urban sustainability

Immigrants' Complementarities and Native Wages: Evidence from California

As of 2004 California employed almost 30% of all foreign born workers in the U.S. and was the state with the largest percentage of immigrants in the labor force. It received a very large number of uneducated immigrants so that two thirds of workers with no schooling degree in California were foreign-born in 2004. If immigration harms the labor opportunities of natives, especially the least skilled ones, California was the place where these effects should have been particularly strong. But is it possible that immigrants raised the demand for California's native workers, rather than harming it? After all immigrants have different skills and tend to work in different occupations then natives and hence they may raise productivity and the demand for complementary production tasks and skills. We consider workers of different education and age as imperfectly substitutable in production and we exploit differences in immigration across these groups to infer their impact on US natives. In order to isolate the "supply-driven" variation of immigrants across skills and to identify the labor market responses of natives we use a novel instrumental variable strategy. Our estimates use migration by skill group to other U.S. states as instrument for migration to California. Migratory flows to other states, in fact, share the same "push" factors as those to California but clearly are not affected by the California-specific "pull" factors. We find that between 1960 and 2004 immigration did not produce a negative migratory response from natives. To the contrary, as immigrants were imperfect substitutes for natives with similar education and age we find that they stimulated, rather than harmed, the demand and wages of most U.S. native workers.

The Dynamics of R&D and Innovation in the Long Run and in the Short Run

In this paper we estimate the dynamic relationship between resources used in R&D by some OECD countries and their innovation output as measured by patent applications. We first estimate a long-run cointegration relation using recently developed tests and panel estimation techniques. We find that the stock of knowledge of a country, its R&D resources and the stock of international knowledge move together in the long run. Then, imposing this long-run relation across variables we analyze the impulse response of new ideas to a shock to R&D or to a shock to innovation by estimating an error correction mechanism. We find that internationally generated ideas have a very significant impact in helping innovation in a country. As a consequence, a positive shock to innovation in a large country as the US has, both in the short and in the long run, a significant positive effect on the innovation of all other countries.Innovation, Panel Cointegration, Error Correction Mechanism

Catching-Up to Foreign Technology? Evidence on the "Veblen-Gerschenkron" Effect of Foreign Investments

The presence of foreign multinational enterprises may benefit local economies. In particular, highly productive foreign-owned firms may promote technological catch-up of local firms. Such channel of spillovers is defined as "Veblen-Geschenkron" effect of Foreign Direct Investments and is analyzed in this article. Rather than the overall density of foreign-owned plants in a region or sector, it is their productivity advantage that determines the positive effect on domestic firms in geographical and technological proximity. We test this hypothesis using new firm-level data for German and Italian manufacturing firms during the 90's. We find evidence of a significant Veblen-Gerschenkron effect which is robust to different ways of measuring total factor productivity (TFP) of firms and to different empirical specifications.

Knowledge Flows and Productivity

National and international flows of knowledge are fundamental determinants of technological progress. In this article we review the existing literature on knowledge flows and we propose a method for estimating them, based on patent citations. Citations are links between inventions that reveal a learning process at the technological frontier. We use data for the period 1975-1996 for 147 subnational regions in Europe and North America. We find that geographical distance and technological differences constitute major barriers to knowledge flows. We also show that these flows may have positive, but small, effect on total factor productivity.

Young People, Skills and Cities

Young highly educated workers developed in the 70’s and 80’s a preference for working in larger cities. As a consequence highly educated young workers in 1990 were over-represented in cities, in spite of the lower wage premium they earned for working in crowded metropolitan areas if compared to their older colleagues. This can be an equilibrium only if young workers enjoy some benefits in cities and are willing to pay for them. In our model, the extra-benefit of working in cities is given by a dynamic externality of human capital. Agglomerations of educated workers arise endogenously, as workers are attracted to dense areas, which improve their learning from others. If the skills accumulated in cities are easily transferable, it is efficient for educated people to work in dense areas while they are young and move to less dense areas when they become mature workers. Once the ”learning period” is over, workers are attracted to smaller and less dense locations where there is less competition from other skilled workers and housing price is lower. Our model explains why young workers were attracted into large cities in the 70’s and 80’s: this was the era of increased flexibility, of the success of versatility rather than specificity of skills. Small firms thrived, and therefore the transferability of skills increased. The model also gives an account of why, once they accumulated their human capital, some of the workers moved to smaller towns.