Social capital and adolescent health risk behavior in El Salvador

An emerging body of research suggests that the social capital available in one's social environment, as defined by supportive and caring interpersonal relationships, may provide a protective effect against a number of youth risk behaviors. In exploring the potential protective effect of social capital at school and at home on adolescent health and social risk behavior, a comprehensive youth risk behavior study was carried out in El Salvador during the summer of 1999 with a sample of 984 secondary school students attending 16 public rural and urban schools. The following dissertation, entitled Social Capital and Adolescent Health Risk Behavior in El Salvador, presents three papers centered on the topics of social capital and risk behavior. ^ Paper #1. Dangers in the Adolescent River of Life: A Descriptive Study of Youth Risk Behavior among Urban and Rural presents prevalence estimates of four principal youth risk behavior domains—aggression, depression, substance use, and sexual behaviors among students primarily between the ages of 13 and 17 who attend public schools in El Salvador. The prevalence and distribution of risk behaviors is examined by gender, geographic school location, age, and subjective economic status. ^ Paper #2. Social Capital and Adolescent Health Risk Behavior among Secondary School Students in El Salvador explores the relationship between social resources (social capital) within the school context and several youth risk behaviors. Results indicated that students who perceived higher social cohesion at school and higher parental social support were significantly less likely to report fighting, having been threatened or hurt with a weapon, suicidal ideation, and sexual intercourse than students with lower perceived social cohesion at school and parental social support after adjusting for several socio-demographic variables. ^ Lastly, paper #3. School Health Environment and Social Capital : Moving beyond the individual to the broader social developmental context provides a theoretical and empirical basis for moving beyond the predominant individual-focus and physical health concerns of school health promotion to the larger social context of schools and social health of students. This paper explores the concept of social capital and relevant adolescent development theories in relation to the influence of social context on adolescent health and behavior. ^

The Improving Relative Status of Black Men

Using data from the Current Population Survey, we examine recent trends in the relative economic status of black men. Our findings point to gains in the relative wages of black men (compared to whites) during the 1990s, especially among younger workers. In 1989, the average black male worker (experienced or not) earned about 69 percent as much per week as the average white male worker. In 2001, the average younger black worker was earning about 86% percent as much as an equally experienced white male; black males at all experience levels earned 72 percent as much as the average white in 2001. Greater occupational diversity and a reduction in unobserved skill differences and/or labor market discrimination explain much of the trend. For both younger and older workers, general wage inequality tempered the rate of wage convergence between blacks and whites during the 1990s, although the effects were less pronounced than during the 1980s.

Body mass index of Vietnamese children ages 6--15 years old

Childhood overweight can increase the risk of chronic diseases later in life. To determine the prevalence, trends and determinants of overweight among children ages 6-15 years old in Vietnam, we assessed data on body mass index (BMI) and demographic and socio-economic characteristics obtained from the 1992 Vietnam Living Standard Survey (1992 VLSS), the 1997 Vietnam Living Standard Survey (1997 VLSS), and the 2000 General Nutrition Survey (2000 GNS). These surveys used multi-stage cluster sample designs to produce nationally representative samples of Vietnamese children ages 6-15 years in 1992-1993, 1997-1998 and 2000. BMI classification was determined using cut-off values set by the International Obesity Task Force (IOTF). The mean prevalence of at risk of overweight and overweight among Vietnamese children rapidly increased from 0.4% in 1992 to 2.0% in 2000, along with a high prevalence of underweight (33.4% in 2000). Increases in weight, height and BMI varied according to gender, area of residence and socioeconomic status. Age, areas of residence and education of the household head are statistically significant predictors of at risk of overweight and overweight. This study identified the prevalence and trends of weight among children crucial to understanding the prevention of child overweight in Vietnam. ^

Differences in health status of HIV infected children cared for by parents as compared to those cared for by grandparents

Purpose. The purpose of the study was to use measures of an HIV positive child's health to examine whether or not there is a difference in their health status according to caretaker and household economic status. ^ Study design. This was a case comparison study between HIV infected children living with parents and those living with grandparents. ^ Study setting. The study was conducted at the Pediatric Infectious Disease Clinic (PIDC) in Mulago, Kampala, Uganda. ^ Participants. 369 HIV-infected children aged seven months to 15 years attending the PIDC between June 13th and August 15th 2007 as well as their caretakers. ^ Method. Patients were recruited during their clinic visits after they had seen the health care providers and waited to receive their medication. Methods used included a survey of all the 369 caregiver participants and abstraction of data from the 369 patient charts. ^ Results. There was no significant association between staging and caretaker status (OR: 0.73 95%CI 0.44–1.21 p=0.09). Children taken care of by grandparents were more likely to have low height for age z-scores and higher weight for height z-scores (OR: 0.32, 95%CI: 0.14–0.74, p = 0.005). There was no difference is social support seeking behavior between parents and grandparents. ^ Conclusion. There was no statistically significant association observed between caretaker status and presenting in advanced stages. This implies that the stage at which HIV-infected children present for care is not determined by the type of caretaker. Caretakers for HIV-infected children need a lot of support beyond medical care. ^

Gastric cancer survival amongst Hispanics- A Hispanic paradox? A case series study using the SEER 1973--2005 data registry

Stomach cancer is the fourth most common cancer in the world, and ranked 16th in the US in 2008. The age-adjusted rates among Hispanics were 2.8 times that of non-Hispanic Whites in 1998-2002. In spite of that, previous research has found that Hispanics with non-cardia adenocarcinoma of the stomach have a slightly better survival than non-Hispanic Whites. However, such previous research did not include a comparison with African-Americans, and it was limited to data released for the years 1973-2000 in the nine original Surveillance, Epidemiology, and End Results Cancer Registries. This finding was interpreted as related to the Hispanic Paradox, a phenomenon that refers to the fact that Hispanics in the USA tend to paradoxically have substantially better health than other ethnic groups in spite of what their aggregate socio-economic indicators would predict. We extended such research to the SEER 17 Registry, 1973-2005, with varying years of diagnosis per registry, and compared the survival of non-cardia adenocarcinoma of the stomach according to ethnicity (Hispanics, non-Hispanic Whites and African-Americans), while controlling for age, gender, marital status, stage of disease and treatment using Cox regression survival analysis. We found that Hispanic ethnicity by itself did not confer an advantage on survival from non-cardia adenocarcinoma of the stomach, but that being born abroad was independently associated with the apparent 'Hispanic Paradox' previously reported, and that such advantage was seen among foreign born persons across all race/ethnic groups.^

Findings of the University of Texas Health Science Center at San Antonio's Dental School pilot mobile van program in Laredo, Texas

Lack of access to oral health care frequently affects those of lower socio-economic level; individuals in this group experience more dental decay, and the caries experience is more likely to be untreated. Inadequate dental care access may be attributed to exclusion that is due to income, geography, age, race or ethnicity. Objective: The present study aims were to: (1) determine how oral disease prevalence and access to dental services in four US-Mexico Border unincorporated low socioeconomic settlements identified as colonias compare to each other and Laredo, Texas, and (2) determine if insurance status affects dental care access and/or disease prevalence. Methods: A secondary analysis of data from a retrospective chart review of 672 patients attending a Mobile Dental Van Program in the Webb County colonias. Demographic information, (ethnicity, age, gender, insurance coverage and colonia site), dental visits within past year, insurance status, presence of dental sealants, prevalence of untreated dental decay (caries), and presence of gum disease (gingivitis and periodontitis) were extracted. Pearson's chi-square tests (χ2) were computed to compare the prevalence of these outcomes between colonias and Laredo and their potential association with insurance status. Results: For 6 - 11 year olds, dental visits in the past year were lower for colonias (39%), than Laredo (58.5%) (p<0.002). Caries prevalence was higher for colonias (56.6%), than Laredo (37.1%) (p<0.001). Gum disease prevalence was higher in colonias (73%), than in Laredo (21.4%) (p<0.001). No significant differences were noted for caries (χ2=1.73; p<0.188) and gum disease (χ2=0.0098; p<0.921) by patient's insurance status. For adults 36 - 64 years of age, dental visits in the past year were lower in colonias (22.4%), than Laredo (36.3%) (p<0.001). Caries prevalence was higher for colonias (78.3%), than Laredo (54.0%) (p<0.001). Gum disease prevalence was also higher among colonias (91.3%) than Laredo (61.3%) (p<0.001). No significant differences were noted for caries (χ2=0.0010; p<0.975) and gum disease (χ2=0.0607; p<0.805) by patient's insurance status. Conclusion: Colonia residents seeking dental care at a Mobile Dental Van Program in Webb County have significantly higher prevalence of oral disease regardless of insurance status.^

A systematic review of literature on socioeconomic disparities in the prevalence of dental caries

Dental caries, also known as tooth decay, are a disease of the oral cavity that affects the tooth structure and leads to the occurrence of cavities in teeth. Dental caries are one of the leading chronic diseases in the population and are very common in childhood. If not treated appropriately, dental caries have debilitating effect on the oral and general health of individuals. ^ Objectives. The aims of this review are to (1) analyze and elucidate the relationship between the social and economic determinants of health like income, education and race/ethnicity and the prevalence of dental caries and (2) identify and understand the pathways/underlying causes through which these factors affect the occurrence of dental caries. This review will provide a foundation for formulation of better oral health policies in future by identifying the key socio-economic factors and pathways affecting the prevalence of dental caries. Knowledge about these socioeconomic factors could be incorporated in the design of future policies and interventions to achieve greater benefits.^ Methods. This review includes information from all pertinent articles, reviews, surveys, reports, peer reviewed literature and web sources that were published after 2000. The selection criterion includes literature focusing on individuals between the ages of 1 to 65 years, and individuals from different subgroups of community based on income, education and race/ethnicity. The analyses of literature include identifying if a relationship between income/education/race and the prevalence of dental caries exists by comparing the prevalence of dental caries in different socio-economic groups. Also included in this review are articles that are relevant to the mechanisms/pathways through which income/education/race affect the prevalence of dental caries.^ Results. Analyses of available literature suggests that disparities in the prevalence of dental caries may be attributed to differences in income, education and race/ethnicity. Higher prevalence of dental caries was observed in African-American and Mexican-American individuals, and in people with low income and low education. The leading pathways through which the socioeconomic factors affect the prevalence of dental caries are the lack of access to dental care, lack of awareness about good oral hygiene beliefs and habits, oral health, inability to afford dental care, lack of social support to maintain oral health and lack of dental insurance.^ Conclusion. Disparities in the prevalence of dental caries exist in various socio-economic groups. The relationship between socio-economic factors and dental caries prevalence should be considered in the development of future policies and interventions that are aimed at reducing the prevalence of dental caries and enhancing oral health status.^

Access to oral care --- A systematic review of a continuing public health issue among older adults

Oral health is essential for the general well being of the individual and collectively for the health of the population. Oral health can be maintained by routine dental care and visits to dental professionals, but accessing professional dental care may be a continuing difficulty in vulnerable older adult population. Many older adults are not frequent users of dental care, though oral health is crucial to their well-being and overall health. Access to care is the timely use of personal health services to achieve the best possible health outcomes. ^ Objectives: The aims of this review are to (i) to analyze and elucidate the relationship between socio-economic disparities in gender, ethnicity, poverty status, education and the continuing public issue of access to oral care, (ii) to identify the underlying causes through which these factors can affect access to oral care. This review will provide a knowledgeable basis for development of interventions to provide adequate access to oral care in older adults and implementing policies to ensure access to oral care; through highlighting the various socio economic factors that affect access to oral care among older adults. ^ Methods: This paper used a purposeful review of literature on socioeconomic disparities in access to oral care among older adults. The references considered in this review included all the relevant articles, surveys and reports published in English language, since the year 1985 to 2010, in the United States. The articles selected were scrutinized for relevancy to the topic of access to oral care and which included discussions of the effects of gender, ethnicity, poverty status, educational status in accessing oral care. ^ Results: Evidence confirmed the continuing disparity in access to oral care among older adults. The possible links identified were gender inequality, ethnic differences, income levels and educational differences affecting access to oral care. The underlying causes linking these factors with access to oral care were established. ^ Conclusion: The analysis of the literature review findings supported the prevalence of disparities in gender, ethnicity, income and education with its possible links affecting access to oral care. The underlying causes helped to understand the reasons behind this growing issue of inaccessible oral care. Further research is needed to develop policies and target dental public health efforts towards specific problem areas ensuring equitable access to oral services and consequently, improve the health of older adults.^

La escasez impuesta : el software libre y el status económico de los bienes inmateriales

Ante el despliegue de posibilidades para crear, reproducir y compartir contenidos que la informática proporciona, surgieron incesantes debates sobre su estatuto económico. Las leyes de propiedad intelectual promulgan medidas cada vez más restrictivas para consumidores y productores, lo que erige barreras a la cultura y favorece monopolios sobredimensionados. Frente a esta situación emergen voces disidentes como el movimiento del software libre. En este artículo, haremos un análisis del debate de los bienes inmateriales, el papel de las leyes de propiedad intelectual y las reivindicaciones del los partidarios del software libre.

Survey on economic assessment of the improvement of the quality of environment: the case of the fight against floods in Cotonou (Benin Living Standard Survey)

This study aims to analyze households' attitude toward flood risk in Cotonou in the sense to identify whether they are willing or not to leave the flood-prone zones. Moreover, the attitudes toward the management of wastes and dirty water are analyzed. The data used in this study were obtained from two sources: the survey implemented during March 2011 on one hundred and fifty randomly selected households living in flood-prone areas of Cotonou, and Benin Living Standard Survey of 2006 (Part relative to Cotonou on 1,586 households). Moreover, climate data were used in this study. Multinomial probability model is used for the econometric analysis of the attitude toward flood risk. While the attitudes toward the management of wastes and dirty water are analyzed through a simple logit. The results show that 55.3% of households agreed to go elsewhere while 44.7% refused [we are better-off here (10.67%), due to the proximity of the activities (19.33), the best way is to build infrastructures that will protect against flood and family house (14.67%)]. The authorities have to rethink an alternative policy to what they have been doing such as building socio-economic houses outside Cotonou and propose to the households that are living the areas prone to inundation. Moreover, access to formal education has to be reinforced.

Measured daily precipitation sums over Central Sulawesi for the period 1981-1999

Data compiled within the IMPENSO project. The Impact of ENSO on Sustainable Water Management and the Decision-Making Community at a Rainforest Margin in Indonesia (IMPENSO), http://www.gwdg.de/~impenso, was a German-Indonesian research project (2003-2007) that has studied the impact of ENSO (El Nino-Southern Oscillation) on the water resources and the agricultural production in the PALU RIVER watershed in Central Sulawesi. ENSO is a climate variability that causes serious droughts in Indonesia and other countries of South-East Asia. The last ENSO event occurred in 1997. As in other regions, many farmers in Central Sulawesi suffered from reduced crop yields and lost their livestock. A better prediction of ENSO and the development of coping strategies would help local communities mitigate the impact of ENSO on rural livelihoods and food security. The IMPENSO project deals with the impact of the climate variability ENSO (El Niño Southern Oscillation) on water resource management and the local communities in the Palu River watershed of Central Sulawesi, Indonesia. The project consists of three interrelated sub-projects, which study the local and regional manifestation of ENSO using the Regional Climate Models REMO and GESIMA (Sub-project A), quantify the impact of ENSO on the availability of water for agriculture and other uses, using the distributed hydrological model WaSiM-ETH (Sub-project B), and analyze the socio-economic impact and the policy implications of ENSO on the basis of a production function analysis, a household vulnerability analysis, and a linear programming model (Sub-project C). The models used in the three sub-projects will be integrated to simulate joint scenarios that are defined in collaboration with local stakeholders and are relevant for the design of coping strategies.

Chapter 6 Economic integration and changes in industrial location in Vietnam

Vietnam has been praised for its achievements in economic growth and success in poverty reduction over the last two decades. The incidence of poverty reportedly fell from 58.1% in 1993 to 19.5% in 2004 (VASS [2006, 13]). The country is also considered to have only a moderate level of aggregate economic inequality by international comparisons. As of the early 2000s, Vietnam’s consumption-based Gini coefficient is found to be comparable to that of other countries with similar levels of per capita GDP. The Gini index did increase between 1993 and 2004, but rather slowly, from 0.34 to 0.37 (VASS [2006, 13]). Yet, as the country moves on with its market oriented reforms, the question of inequality has been highlighted in policy and academic discourses. In particular, it is pointed out that socio-economic inequalities between regions (or provinces) are significant and have been widening behind aggregate figures (NCSSH [2001], Mekong Economics [2005], VASS [2006]). Between 1993 and 2004, while real per capita expenditure increased in all regions, it grew fastest in those regions with the highest per capita expenditures and vice versa, resulting in greater regional disparities (VASS [2006, 37]). A major contributing factor to such regional inequalities is the uneven distribution of industry within the country. According to the Statistical Yearbook of Vietnam, of the country's gross industrial output in 2007, over 50% belongs to the South East region, close to 25% to the Red River Delta, and about 10% to the Mekong River Delta. All remaining regions share some 10% of the country's gross industrial output. At a quick glance, the South East increased its share of the total industrial gross output in the 1990s, while the Red River Delta started to gain ground in more recent years. How can the government deal with regional disparities is a valid question. In order to offer an answer, it is necessary in the first place to grasp the trend of disparities as well as its background. To that end, this paper is a preparatory endeavor. Regional disparities in industrial activities can essentially be seen as a result of the location decisions of enterprises. While the General Statistics Office (GSO) of Vietnam has conducted one enterprise census (followed by annual enterprise surveys) and two stages of establishment censuses since 2000, sectorally and geographically disaggregated data are not readily available. Therefore, for the moment, we will draw on earlier studies of industrial location and the determinants of enterprises’ location decisions in Vietnam. The remainder of this paper is structured as follows. The following two sections deal with the country context. Section 2 will outline some major developments in Vietnam’s international economic relations that may affect sub-national location of industry. According to the theory of spatial economics, economic integration is seen as a major driver of changes in industrial location, both between and within countries (Nishikimi [2008]). Section 3, on the other hand, will consider some possible factors affecting geographic distribution of industry in the domestic sphere. In Section 4, existing literature on industrial and firm location will be examined, and Section 5 will briefly summarize the findings and suggest some areas for future research.

Integrated economic-hydrologic analysis of policy responses

Water is a vital resource, but also a critical limiting factor for economic and social development in many parts of the world. The recent rapid growth in human population and water use for social and economic development is increasing the pressure on water resources and the environment, as well as leading to growing conflicts among competing water use sectors (agriculture, urban, tourism, industry) and regions (Gleick et al., 2009; World Bank, 2006). In Spain, as in many other arid and semi-arid regions affected by drought and wide climate variability, irrigated agriculture is responsible for most consumptive water use and plays an important role in sustaining rural livelihoods (Varela-Ortega, 2007). Historically, the evolution of irrigation has been based on publicly-funded irrigation development plans that promoted economic growth and improved the socio-economic conditions of rural farmers in agrarian Spain, but increased environmental damage and led to excessive and inefficient exploitation of water resources (Garrido and Llamas, 2010; Varela-Ortega et al., 2010). Currently, water policies in Spain focus on rehabilitating and improving the efficiency of irrigation systems, and are moving from technocratic towards integrated water management strategies driven by the European Union (EU) Water Framework Directive (WFD).

The Extended Water Footprint and illegal groundwater use in the Upper Guadiana Basin (Spain)

Tablas de Daimiel National Park is located in the Upper Guadiana Basin and represents one of the largest and most important wetlands in Europe. The long term ecological integrity of this wetland is inherently associated with the maintenance of a shallow groundwater table, namely the Western Mancha aquifer (WMA) or Aquifer 23. The intensive use of groundwater, mainly for irrigation, has led over the last decades to deep socio‐economic changes. Such intensive use has also lowered the water table of Aquifer 23, drastically reducing the flooded area of the wetland and threatening its ecological integrity. A number of plans and measures have been developed and implemented since the declaration of overexploitation of Aquifer 23 in the year 1987. The most recent one is the Special Plan for the Upper Guadiana (SPUG), approved in 2008. This Plan is the main measure to comply with achieving the objective of good quantitative and qualitative status required under the Water Framework Directive (2000). This paper offers a new type of integrated analysis which allows assessing under a common lens the physical, economic and social dimensions of groundwater use in the area. The first objective is to calculate the groundwater footprint of agricultural production in the Upper Guadiana basin and its evolution during 2000‐2008. For this purpose, we have applied the Extended Water Footprint (EWF) methodology ‐a novel approach based on the classical Water Footprint (WF) approach‐ that includes an assessment of the water productivity from an economic and social perspective. Compared to the classical WF, the EWF allows for a more complete overview of the sector, providing new insights for policy decisions (e.g. to define options and possibilities on water re‐allocation in order to achieve both better ecosystem conservation and social equity). The second objective is to use the EWF to compare the existing authorized and non‐authorized or illegal use of water. This allows us to discuss current initiatives by public authorities in relation to the existing frame of water rights

Análisis de los factores de adopción de comercio electrónico en segmentos de consumidores finales. Aplicación al caso español

El comercio electrónico ha experimentado un fuerte crecimiento en los últimos años, favorecido especialmente por el aumento de las tasas de penetración de Internet en todo el mundo. Sin embargo, no todos los países están evolucionando de la misma manera, con un espectro que va desde las naciones pioneras en desarrollo de tecnologías de la información y comunicaciones, que cuentan con una elevado porcentaje de internautas y de compradores online, hasta las rezagadas de rápida adopción en las que, pese a contar con una menor penetración de acceso, presentan una alta tasa de internautas compradores. Entre ambos extremos se encuentran países como España que, aunque alcanzó hace años una tasa considerable de penetración de usuarios de Internet, no ha conseguido una buena tasa de transformación de internautas en compradores. Pese a que el comercio electrónico ha experimentado importantes aumentos en los últimos años, sus tasas de crecimiento siguen estando por debajo de países con características socio-económicas similares. Para intentar conocer las razones que afectan a la adopción del comercio por parte de los compradores, la investigación científica del fenómeno ha empleado diferentes enfoques teóricos. De entre todos ellos ha destacado el uso de los modelos de adopción, proveniente de la literatura de adopción de sistemas de información en entornos organizativos. Estos modelos se basan en las percepciones de los compradores para determinar qué factores pueden predecir mejor la intención de compra y, en consecuencia, la conducta real de compra de los usuarios. Pese a que en los últimos años han proliferado los trabajos de investigación que aplican los modelos de adopción al comercio electrónico, casi todos tratan de validar sus hipótesis mediante el análisis de muestras de consumidores tratadas como un único conjunto, y del que se obtienen conclusiones generales. Sin embargo, desde el origen del marketing, y en especial a partir de la segunda mitad del siglo XIX, se considera que existen diferencias en el comportamiento de los consumidores, que pueden ser debidas a características demográficas, sociológicas o psicológicas. Estas diferencias se traducen en necesidades distintas, que sólo podrán ser satisfechas con una oferta adaptada por parte de los vendedores. Además, por contar el comercio electrónico con unas características particulares que lo diferencian del comercio tradicional –especialmente por la falta de contacto físico entre el comprador y el producto– a las diferencias en la adopción para cada consumidor se le añaden las diferencias derivadas del tipo de producto adquirido, que si bien habían sido consideradas en el canal físico, en el comercio electrónico cobran especial relevancia. A la vista de todo ello, el presente trabajo pretende abordar el estudio de los factores determinantes de la intención de compra y la conducta real de compra en comercio electrónico por parte del consumidor final español, teniendo en cuenta el tipo de segmento al que pertenezca dicho comprador y el tipo de producto considerado. Para ello, el trabajo contiene ocho apartados entre los que se encuentran cuatro bloques teóricos y tres bloques empíricos, además de las conclusiones. Estos bloques dan lugar a los siguientes ocho capítulos por orden de aparición en el trabajo: introducción, situación del comercio electrónico, modelos de adopción de tecnología, segmentación en comercio electrónico, diseño previo del trabajo empírico, diseño de la investigación, análisis de los resultados y conclusiones. El capítulo introductorio justifica la relevancia de la investigación, además de fijar los objetivos, la metodología y las fases seguidas para el desarrollo del trabajo. La justificación se complementa con el segundo capítulo, que cuenta con dos elementos principales: en primer lugar se define el concepto de comercio electrónico y se hace una breve retrospectiva desde sus orígenes hasta la situación actual en un contexto global; en segundo lugar, el análisis estudia la evolución del comercio electrónico en España, mostrando su desarrollo y situación presente a partir de sus principales indicadores. Este apartado no sólo permite conocer el contexto de la investigación, sino que además permite contrastar la relevancia de la muestra utilizada en el presente estudio con el perfil español respecto al comercio electrónico. Los capítulos tercero –modelos de adopción de tecnologías– y cuarto –segmentación en comercio electrónico– sientan las bases teóricas necesarias para abordar el estudio. En el capítulo tres se hace una revisión general de la literatura de modelos de adopción de tecnología y, en particular, de los modelos de adopción empleados en el ámbito del comercio electrónico. El resultado de dicha revisión deriva en la construcción de un modelo adaptado basado en los modelos UTAUT (Unified Theory of Acceptance and Use of Technology, Teoría unificada de la aceptación y el uso de la tecnología) y UTAUT2, combinado con dos factores específicos de adopción del comercio electrónico: el riesgo percibido y la confianza percibida. Por su parte, en el capítulo cuatro se revisan las metodologías de segmentación de clientes y productos empleadas en la literatura. De dicha revisión se obtienen un amplio conjunto de variables de las que finalmente se escogen nueve variables de clasificación que se consideran adecuadas tanto por su adaptación al contexto del comercio electrónico como por su adecuación a las características de la muestra empleada para validar el modelo. Las nueve variables se agrupan en tres conjuntos: variables de tipo socio-demográfico –género, edad, nivel de estudios, nivel de ingresos, tamaño de la unidad familiar y estado civil–, de comportamiento de compra – experiencia de compra por Internet y frecuencia de compra por Internet– y de tipo psicográfico –motivaciones de compra por Internet. La segunda parte del capítulo cuatro se dedica a la revisión de los criterios empleados en la literatura para la clasificación de los productos en el contexto del comercio electrónico. De dicha revisión se obtienen quince grupos de variables que pueden tomar un total de treinta y cuatro valores, lo que deriva en un elevado número de combinaciones posibles. Sin embargo, pese a haber sido utilizados en el contexto del comercio electrónico, no en todos los casos se ha comprobado la influencia de dichas variables respecto a la intención de compra o la conducta real de compra por Internet; por este motivo, y con el objetivo de definir una clasificación robusta y abordable de tipos de productos, en el capitulo cinco se lleva a cabo una validación de las variables de clasificación de productos mediante un experimento previo con 207 muestras. Seleccionando sólo aquellas variables objetivas que no dependan de la interpretación personal del consumidores y que determinen grupos significativamente distintos respecto a la intención y conducta de compra de los consumidores, se obtiene un modelo de dos variables que combinadas dan lugar a cuatro tipos de productos: bien digital, bien no digital, servicio digital y servicio no digital. Definidos el modelo de adopción y los criterios de segmentación de consumidores y productos, en el sexto capítulo se desarrolla el modelo completo de investigación formado por un conjunto de hipótesis obtenidas de la revisión de la literatura de los capítulos anteriores, en las que se definen las hipótesis de investigación con respecto a las influencias esperadas de las variables de segmentación sobre las relaciones del modelo de adopción. Este modelo confiere a la investigación un carácter social y de tipo fundamentalmente exploratorio, en el que en muchos casos ni siquiera se han encontrado evidencias empíricas previas que permitan el enunciado de hipótesis sobre la influencia de determinadas variables de segmentación. El capítulo seis contiene además la descripción del instrumento de medida empleado en la investigación, conformado por un total de 125 preguntas y sus correspondientes escalas de medida, así como la descripción de la muestra representativa empleada en la validación del modelo, compuesta por un grupo de 817 personas españolas o residentes en España. El capítulo siete constituye el núcleo del análisis empírico del trabajo de investigación, que se compone de dos elementos fundamentales. Primeramente se describen las técnicas estadísticas aplicadas para el estudio de los datos que, dada la complejidad del análisis, se dividen en tres grupos fundamentales: Método de mínimos cuadrados parciales (PLS, Partial Least Squares): herramienta estadística de análisis multivariante con capacidad de análisis predictivo que se emplea en la determinación de las relaciones estructurales de los modelos propuestos. Análisis multigrupo: conjunto de técnicas que permiten comparar los resultados obtenidos con el método PLS entre dos o más grupos derivados del uso de una o más variables de segmentación. En este caso se emplean cinco métodos de comparación, lo que permite asimismo comparar los rendimientos de cada uno de los métodos. Determinación de segmentos no identificados a priori: en el caso de algunas de las variables de segmentación no existe un criterio de clasificación definido a priori, sino que se obtiene a partir de la aplicación de técnicas estadísticas de clasificación. En este caso se emplean dos técnicas fundamentales: análisis de componentes principales –dado el elevado número de variables empleadas para la clasificación– y análisis clúster –del que se combina una técnica jerárquica que calcula el número óptimo de segmentos, con una técnica por etapas que es más eficiente en la clasificación, pero exige conocer el número de clústeres a priori. La aplicación de dichas técnicas estadísticas sobre los modelos resultantes de considerar los distintos criterios de segmentación, tanto de clientes como de productos, da lugar al análisis de un total de 128 modelos de adopción de comercio electrónico y 65 comparaciones multigrupo, cuyos resultados y principales consideraciones son elaboradas a lo largo del capítulo. Para concluir, el capítulo ocho recoge las conclusiones del trabajo divididas en cuatro partes diferenciadas. En primer lugar se examina el grado de alcance de los objetivos planteados al inicio de la investigación; después se desarrollan las principales contribuciones que este trabajo aporta tanto desde el punto de vista metodológico, como desde los punto de vista teórico y práctico; en tercer lugar, se profundiza en las conclusiones derivadas del estudio empírico, que se clasifican según los criterios de segmentación empleados, y que combinan resultados confirmatorios y exploratorios; por último, el trabajo recopila las principales limitaciones de la investigación, tanto de carácter teórico como empírico, así como aquellos aspectos que no habiendo podido plantearse dentro del contexto de este estudio, o como consecuencia de los resultados alcanzados, se presentan como líneas futuras de investigación. ABSTRACT Favoured by an increase of Internet penetration rates across the globe, electronic commerce has experienced a rapid growth over the last few years. Nevertheless, adoption of electronic commerce has differed from one country to another. On one hand, it has been observed that countries leading e-commerce adoption have a large percentage of Internet users as well as of online purchasers; on the other hand, other markets, despite having a low percentage of Internet users, show a high percentage of online buyers. Halfway between those two ends of the spectrum, we find countries such as Spain which, despite having moderately high Internet penetration rates and similar socio-economic characteristics as some of the leading countries, have failed to turn Internet users into active online buyers. Several theoretical approaches have been taken in an attempt to define the factors that influence the use of electronic commerce systems by customers. One of the betterknown frameworks to characterize adoption factors is the acceptance modelling theory, which is derived from the information systems adoption in organizational environments. These models are based on individual perceptions on which factors determine purchase intention, as a mean to explain users’ actual purchasing behaviour. Even though research on electronic commerce adoption models has increased in terms of volume and scope over the last years, the majority of studies validate their hypothesis by using a single sample of consumers from which they obtain general conclusions. Nevertheless, since the birth of marketing, and more specifically from the second half of the 19th century, differences in consumer behaviour owing to demographic, sociologic and psychological characteristics have also been taken into account. And such differences are generally translated into different needs that can only be satisfied when sellers adapt their offer to their target market. Electronic commerce has a number of features that makes it different when compared to traditional commerce; the best example of this is the lack of physical contact between customers and products, and between customers and vendors. Other than that, some differences that depend on the type of product may also play an important role in electronic commerce. From all the above, the present research aims to address the study of the main factors influencing purchase intention and actual purchase behaviour in electronic commerce by Spanish end-consumers, taking into consideration both the customer group to which they belong and the type of product being purchased. In order to achieve this goal, this Thesis is structured in eight chapters: four theoretical sections, three empirical blocks and a final section summarizing the conclusions derived from the research. The chapters are arranged in sequence as follows: introduction, current state of electronic commerce, technology adoption models, electronic commerce segmentation, preliminary design of the empirical work, research design, data analysis and results, and conclusions. The introductory chapter offers a detailed justification of the relevance of this study in the context of e-commerce adoption research; it also sets out the objectives, methodology and research stages. The second chapter further expands and complements the introductory chapter, focusing on two elements: the concept of electronic commerce and its evolution from a general point of view, and the evolution of electronic commerce in Spain and main indicators of adoption. This section is intended to allow the reader to understand the research context, and also to serve as a basis to justify the relevance and representativeness of the sample used in this study. Chapters three (technology acceptance models) and four (segmentation in electronic commerce) set the theoretical foundations for the study. Chapter 3 presents a thorough literature review of technology adoption modelling, focusing on previous studies on electronic commerce acceptance. As a result of the literature review, the research framework is built upon a model based on UTAUT (Unified Theory of Acceptance and Use of Technology) and its evolution, UTAUT2, including two specific electronic commerce adoption factors: perceived risk and perceived trust. Chapter 4 deals with client and product segmentation methodologies used by experts. From the literature review, a wide range of classification variables is studied, and a shortlist of nine classification variables has been selected for inclusion in the research. The criteria for variable selection were their adequacy to electronic commerce characteristics, as well as adequacy to the sample characteristics. The nine variables have been classified in three groups: socio-demographic (gender, age, education level, income, family size and relationship status), behavioural (experience in electronic commerce and frequency of purchase) and psychographic (online purchase motivations) variables. The second half of chapter 4 is devoted to a review of the product classification criteria in electronic commerce. The review has led to the identification of a final set of fifteen groups of variables, whose combination offered a total of thirty-four possible outputs. However, due to the lack of empirical evidence in the context of electronic commerce, further investigation on the validity of this set of product classifications was deemed necessary. For this reason, chapter 5 proposes an empirical study to test the different product classification variables with 207 samples. A selection of product classifications including only those variables that are objective, able to identify distinct groups and not dependent on consumers’ point of view, led to a final classification of products which consisted on two groups of variables for the final empirical study. The combination of these two groups gave rise to four types of products: digital and non-digital goods, and digital and non-digital services. Chapter six characterizes the research –social, exploratory research– and presents the final research model and research hypotheses. The exploratory nature of the research becomes patent in instances where no prior empirical evidence on the influence of certain segmentation variables was found. Chapter six also includes the description of the measurement instrument used in the research, consisting of a total of 125 questions –and the measurement scales associated to each of them– as well as the description of the sample used for model validation (consisting of 817 Spanish residents). Chapter 7 is the core of the empirical analysis performed to validate the research model, and it is divided into two separate parts: description of the statistical techniques used for data analysis, and actual data analysis and results. The first part is structured in three different blocks: Partial Least Squares Method (PLS): the multi-variable analysis is a statistical method used to determine structural relationships of models and their predictive validity; Multi-group analysis: a set of techniques that allow comparing the outcomes of PLS analysis between two or more groups, by using one or more segmentation variables. More specifically, five comparison methods were used, which additionally gives the opportunity to assess the efficiency of each method. Determination of a priori undefined segments: in some cases, classification criteria did not necessarily exist for some segmentation variables, such as customer motivations. In these cases, the application of statistical classification techniques is required. For this study, two main classification techniques were used sequentially: principal component factor analysis –in order to reduce the number of variables– and cluster analysis. The application of the statistical methods to the models derived from the inclusion of the various segmentation criteria –for both clients and products–, led to the analysis of 128 different electronic commerce adoption models and 65 multi group comparisons. Finally, chapter 8 summarizes the conclusions from the research, divided into four parts: first, an assessment of the degree of achievement of the different research objectives is offered; then, methodological, theoretical and practical implications of the research are drawn; this is followed by a discussion on the results from the empirical study –based on the segmentation criteria for the research–; fourth, and last, the main limitations of the research –both empirical and theoretical– as well as future avenues of research are detailed.