Compatriots or Competitors? Job Competition between Foreign- and U.S.-born Angelenos

The debate concerning job competition between immigrant and nonimmigrant groups has intensified owing to the large increase in the 1970s and 1980s in immigration and the simultaneous growth in urban poverty rates for African-American and other minority groups. It focuses on the possible wage and displacement effects an increase in immigration would cause for the U.S.-born population. Using 1970 and 1980 industrial and occupational census data and shift-share methodology for Los Angeles, the author shows that immigrants do not simply function as either competitive or complementary sources of labor. Instead, he argues, job competition between groups of workers depends in part on whether U.S.-born workers belong to protected or unprotected labor markets. Overall, the data in this study reveal that immigrants are not displacing native-born labor in disproportionate numbers, especially in industries. However, there are isolated instances of job displacement between immigrants and native-born whites and Mexicans in some occupations. In addition, complementarity (e.g., job growth) is more frequent than displacement in industries and occupations, and decreases in white employment are not the net result of immigrant employment growth in Los Angeles

Geographical and occupational concentration of Puerto Rican migration to the United States, 1982-1986

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 1988.Title as it appeared in MIT Graduate List, June 1988: Labor market consequences of immigration : a study of recent Puerto Rican migrants in select occupations and cities in the U.S.Includes bibliographical references.by Abel Valenzuela, Jr.M.C.P

Day labor, informality and vulnerability in South Africa and the United States

The purpose of this paper is to compare conditions in informal day-labor markets in South Africa and the USA to better understand the nature of worker vulnerabilities in this market, as well as the economic conditions that have contributed to the growth of day labor. The conclusion considers interventions that are underway in the two countries to improve conditions in day-labor markets.– The paper is based on national surveys of day laborers in South Africa and the USA. A random sample of day laborers seeking work at informal hiring sites was undertaken in each country. The paper presents key findings, compares conditions in South Africa and the USA, and analyzes the relationship between economic change, labor-market dynamics, and worker vulnerability

Aberrant Water Homeostasis Detected by Stable Isotope Analysis

While isotopes are frequently used as tracers in investigations of disease physiology (i.e., 14C labeled glucose), few studies have examined the impact that disease, and disease-related alterations in metabolism, may have on stable isotope ratios at natural abundance levels. The isotopic composition of body water is heavily influenced by water metabolism and dietary patterns and may provide a platform for disease detection. By utilizing a model of streptozotocin (STZ)-induced diabetes as an index case of aberrant water homeostasis, we demonstrate that untreated diabetes mellitus results in distinct combinations, or signatures, of the hydrogen (δ2H) and oxygen (δ18O) isotope ratios in body water. Additionally, we show that the δ2H and δ18O values of body water are correlated with increased water flux, suggesting altered blood osmolality, due to hyperglycemia, as the mechanism behind this correlation. Further, we present a mathematical model describing the impact of water flux on the isotopic composition of body water and compare model predicted values with actual values. These data highlight the importance of factors such as water flux and energy expenditure on predictive models of body water and additionally provide a framework for using naturally occurring stable isotope ratios to monitor diseases that impact water homeostasis

Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates

Unidad de excelencia María de Maeztu CEX2019-000940-MAim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period: Tree-inventory plots established between 1934 and 2019. Major taxa studied: Trees with a diameter at breast height (DBH) ≥ 9.55 cm. Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types

Compatriots or Competitors?: A Study of Job Competition Between the Foreign-born and Native in Los Angeles, 1970-1980

The current debate concerning job competition between immigrant and nonimmigrant has intensified because of the large increase in immigration and the simultaneous growth in urban poverty rates for African Americans and other ethnic minority groups during the 1970s. The debate focuses on the possible wage and displacement effects that an increase in immigration would cause for the U.S.-born population. Empirical research on the displacement effects of increased immigration focuses on aggregate, national samples, industrial and occupational sectoral studies, and analysis of labor market outcomes across differences and never considers industrial change (i.e., growth or decline) and institutional barriers, such as high-skilled and low-skilled labor markets.Using 1970 and 1980 census data (PUS and PUMS files, respectively) for Los Angeles, by specific types of labor markets (industries and occupations), and according to race and ethnicity (white, black, Mexican, Latino, and Asian) and nativity (foreign-born and U.S.-born), I argue that immigrants do not simply function as either competitive or complementary sources of labor. Instead, I hypothesize that job competition between groups of workers depends in part on whether U.S.-born workers belong to protected or unprotected labor markets and whether they are employed in growing or declining industries.Based on the results of this study, I conclude that segmentation/queuing theory best describes the labor market processes between immigrant and native-born labor in Los Angeles during 1970 and 1980. Overall, the data in this study show that immigrants are not displacing native-born labor in disproportionate numbers, especially in industries. Instances are found, however, of isolated job displacement between immigrants and native-born whites and/or Mexicans in occupations. The data also show that complementarity is more frequent than displacement and that decreases in white labor are not the result of immigrant employment growth. These two findings taken together suggest a process of job queuing assert that immigration is not a major contributor to a black and Latino underclass in Los Angle

Working on the Margins in Metropolitan Los Angeles: Immigrants in Day-Labor Work

Este artículo explora la teoría de la desventaja para entender la participación de inmigrantes latinos como jornaleros urbanos. Entrevistas con 481 jornaleros urbanos, seleccionados aleatoriamente en 87 lugares de empleo en el área metropolitana de Los Ángeles, hacen posible un análisis de las características demográficas y del mercado de trabajo de este tipo de auto empleados. Aunque la gran mayoría de los jornaleros urbanos son inmigrantes recién llegados sin autorización para trabajar, no todos están desesperados, como la teoría de la desventaja podría hacernos creer. Los jornaleros urbanos son diversos en términos de su estructura familiar, el tiempo de su llegada, su experiencia en este trabajo y su capital humano. A pesar de esto, la falta de capital humano y otras características, generalmente los obstaculizan para buscar ocupaciones estables y mejor pagadas en el mercado laboral regular. Los ingresos entre los jornaleros urbanos son diversos, la paga por hora es mayor que los topes del salario mínimo federal o estatal, el regateo de salarios es común y ven-tajoso para el trabajador y los salarios son pagados en efectivo y libres de impuestos. Sin embargo, estas ventajas son neutralizadas por la inestabilidad del trabajo. Para una minoría de jornaleros urbanos este mercado ofrece una alternativa a otros empleos irregulares y de baja calificación