Este trabalho tem como objetivo analisar o impacto da oferta e da demanda por trabalho qualificado sobre o diferencial de salários entre trabalhadores de elevada e baixa qualificação para o Brasil, durante o período de 1992 a 2009. Para tanto, foi utilizado um modelo microeconômico de oferta e demanda por trabalho qualificado, sendo que a qualificação é determinada pelos anos completos de escolaridade. Dessa maneira, foi constatada uma elevação do diferencial de salários entre o trabalho de elevada qualificação (com ensino superior) e baixa qualificação (com ensino médio ou ensino básico) no período de 1992 a 2001, que foi impulsionada pelo efeito da demanda por trabalho qualificado. Por sua vez, no período de 2002 a 2009, foi constatada uma pequena diminuição desse diferencial, determinada pela intensificação da oferta relativa de trabalho qualificado que ocorreu durante esse período. / The objective of this dissertation is to assess the impact of supply and demand for skills in the wage differentials between skilled and unskilled workers in Brazil, during 1992 and 2009. To do so, a microeconomic model of supply and demand for skill was used where a worker\'s skill is directly linked with its educational level. In this matter, a rise in the skill premium (wage differentials between college and less than college workers) was observed between 1992 and 2001, driven by the demand for skilled labor. Adversely, during 2002 and 2009, a slight decrease in the skill premium was observed which was driven by the intensification of the relative supply of skilled workers.

A critical evaluation of the national profile of energy supply and demand and the associated greenhouse gas (OHO) emissions in China has been conducted. The contribution of the transport sector in China, the road transport sector in particular, to China's overall energy demand and OHO emissions has been assessed and compared with values for other countries. Approaches for reducing energy demand and OHO emissions in the road transport sector worldwide have been reviewed. A detailed bottom-up model has been developed using 'LEAP' software, to estimate future energy demand and OHO emissions in China's road transport sector, incorporating China's recent efforts in alternative fuel promotion. Modelling approach and historical data used have been tested and verified to ensure reliability. Two scenarios have been designed to describe the future strategies relating to the development of China's road transport sector between 2005 and 2030. The 'Business as Usual' scenario is used as a baseline reference scenario, in which the government is assumed to do nothing to influence the long-term trends of road transport energy demand. The 'Best Case' scenario is considered to be the most optimized case where a series of available reduction measures are assumed to be implemented. Energy demand and OHO emissions in China's road transport sector up to 2030 are estimated in these two scenarios. The reduction potential and the relative contribution of each measure have been estimated. A 'life cycle assessment' model for the road transport sector has been developed. The life cycle energy demand and OHO emissions in China's road transport sector are estimated using the model. The reduction potential and the relative contribution of each measure have been re-assessed from a life cycle perspective. Potential impacts on global oil resources, availability and prices are discussed. The importance of life cycle assessment in evaluating the effects of different reduction measures is discussed. Policy implications are presented.

O turismo entrou em um período de forte expansão após a Segunda Guerra Mundial que perdura até os dias atuais. O aumento da circulação de turistas repercute na geração de renda e empregos para os países visitados, além do enriquecimento adquirido através das trocas culturais. Este crescimento tem despertado o interesse da comunidade científica, bem como profissional, com o intuito de explorar as metodologias para a modelagem e previsão da demanda turística. Estimativas acuradas da demanda servem de apoio para corretas tomadas de decisão por parte dos gestores quanto ao dimensionamento adequado de recursos financeiros, especialmente frente à realização de um evento de grandes proporções. Neste sentido, este trabalho tem por objetivos verificar quais são as técnicas atualmente mais utilizadas para previsão de demandas turísticas através de revisão da literatura, desde 2005 até 2015; utilizar dois métodos de modelagem (ARIMA e RNA) para modelar e prever a demanda turística de duas sedes olímpicas recentes; comparar essas previsões com as previsões obtidas por cinco métodos de combinação de previsões (médias aritmética, harmônica e geométrica, variância mínima e regressão linear) e; aplicar o método mais acurado para prever a demanda turística do Brasil. Os resultados foram avaliados através de três medidas de acurácia. Em virtude da realização dos Jogos Olímpicos em 2016, a demanda brasileira para este período foi modelada e prevista e a previsão foi ajustada segundo um ajuste matemático sazonal, objetivando ganho de acurácia. Foi observado ganho de acurácia quando as previsões foram combinadas e, na série brasileira, o ajuste adotado indicou um acréscimo de 175% na demanda original para agosto de 2016. / Tourism has experienced a strong increase since the end of World War II. The increase in tourist circulation results in income and employment expansion, besides the cultural enrichment involved in such experiences. This growth has attracted attention from the scientific community as well as professional, with the objective of exploring the methodologies for tourism demand modelling and forecasts. Accurate demand estimates serve as support for correct decision making by managers especially considering financial resource scaling for major events. In this sense, this study aims to verify which techniques are more currently used for forecasting tourism demand through review of the literature from 2005 to 2015; using two modeling methods (ARIMA and ANN) to make models and forecasting the tourism demand of two recent Olympic hosts; comparing these forecasts with the forecasts obtained for five methods of combining forecasts (arithmetic, harmonic and geometric means, minimum variance and linear regression) and; applying the most accurated method to forecast the tourism demand in Brazil. The results were evaluated using three different accuracy measurements. By virtue of the 2016 Olympic Games, the Brazilian tourism demand was modeled and the forecast was adjusted by a seasonal mathematical adjustment, designed for better precision. A gain in preciseness was observed when forecasts were combined and, for the Brazilian series, the adopted adjustment indicated an increase of 175% when compared with the original demand for August 2016.

Esta tese tem como objetivo compreender as práticas relacionadas ao consumo de produtos audiovisuais sob demanda em plataformas digitais através da investigação das práticas relacionadas à Netflix na rotina dos seus usuários. O referencial teórico toma como base a Teoria da Prática, na qual a prática é considerada um comportamento rotinizado, com vários elementos interconectados, em uma relação constante entre agentes e objetos. O estudo empírico acontece a partir de entrevistas semiestruturadas e observação dos espaços de consumo — os respondentes foram selecionados por meio de um questionário prévio compartilhado em sites de redes sociais. A investigação acontece com base em cinco eixos: materiais, competências, dinâmicas afetivas, relacionais e espaço-temporais. Em termos gerais, conclui-se que o consumo de conteúdo na Netflix e as práticas relacionadas adquiriram ao longo do tempo um caráter social e recursivo, e assumem também uma dimensão afetiva no cotidiano dos usuários. Nesse sentido, nota-se também o estabelecimento e a reprodução de fluxos de consumo interconectados, nos quais usuários e empresa relacionam-se continuamente: de um lado, há a disponibilização contínua de conteúdo, e do outro, o acesso rotinizado, fragmentado e marcado pela insaciabilidade e autonomia do tempo dedicado à prática, o que favorece a manutenção da estrutura. / The aim of this study is to understand consumption habits of on-demand audiovisual products available on digital platforms by investigating how Netflix is incorporated into the routines of its subscribers. The theoretical reference is based on the practice theory, where the practice is a routine behavior with many interconnected elements of a constant relationship between agents and objects. The empirical research is comprised of semi-structured interviews and by observing spaces of consumption – the respondents were selected from a survey made available on social network sites. The research is based on five axes: materials, skills, affective dynamics, relational and space-time. Overall, it is concluded that content consumption in Netflix and related practices acquired a social and recursive character over time, assuming an affective dimension. In this respect, users and companies are constantly relating with one another in a flowing exchange of interconnected consumption. On one hand, there is constant access to content; on the other, there is routine access which can be fragmented and determined by one’s insatiableness and how much time is spent on it, a key to maintaining its structure.

Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Economics. / Vita. / Bibliography: leaves 213-214. / Ph.D.

The field of International Trade aims to study the consequences of the spatial disconnection between the activities of production and consumption, which has been allowed by the increasing opening of the economies. However, while most of the history of the field has focused on the role played by production in shaping trade patterns, only recently researchers have emphasized the importance of demand characteristics. This dissertation follows these recent works by containing three essays that specifically study the importance of demand characteristics on export patterns at the microeconomic level. In the first chapter of this dissertation, I explore the importance of the dynamic aspects of demand on the export decisions made by firms. Standard dynamic models of trade identify sunk entry costs as the main export barrier faced by firms. However, these large entry costs are inconsistent with the existence of many small new exporters with low survival rates in foreign markets. In this chapter, I study the role of destination-specific demand dynamics by introducing, in a dynamic model of trade, the idea that firms gradually accumulate consumers in foreign markets. Estimating the model using export data from individual French firms, I show that this consumer margin is consistent with the dynamics of sales, prices and survival of exporters, but also leads to much lower estimates of the entry costs of exporting - about one third of those estimated in the standard model. Moreover, this change in the nature of trade barriers has important implications at the aggregate level. In contrast to the standard model, this model correctly replicates the slow response of trade to shocks and the increasing contribution of the extensive margin in this response. Finally, I demonstrate using out-of-sample predictions that the model better predicts actual trade responses to an observed shock than the standard model. The second chapter presents a novel instrumental variable strategy to estimate product quality at the micro level using trade data. Written with Gabriel Smagghue from University Carlos III of Madrid, this work develops a new firm-specific instrument, based on variations in exchange rates combined with firm-specific import shares, that delivers, under weak assumptions, consistent estimates of demand elasticity and firm product quality. Implementing our method using French customs data, we document the reliability of these measures through correlations with firm characteristics and alternative measures of quality. Finally, we use our estimates to document the quality response of French firms when facing low-wage competition on foreign markets. Finally, in the third chapter of this dissertation, I document the positive correlation between the size of a firm and its advertising intensity - measured by the amount spent in advertising as percentages of sales. Taking advantage of firm-level information about advertising expenditures from the Chilean manufacturing census, I show that this correlation holds between firms operating within a similar industry, and is stronger in industries with a larger scope for vertical differentiation. Building on these findings, I develop a model of advertising with heterogeneous firms, based on Arkolakis (2010). In addition to using advertising to inform consumers about the existence of their good, firms can use advertising to affect consumers' valuation of their products. Consistent with the empirical findings, this latter feature of advertising leads to a positive link between the advertising intensity of a firm and its size. Moreover, this link is amplified by a parameter describing the degree of vertical differentiation of the product.

This dissertation consists of three papers in revenue management: on-line assortment optimization with reusable resources, spatial distribution of surge price under incentive compatible assignment for drivers and optimal price rebates for demand response under power flow constraints. In Chapter 2, we study an on-line assortment optimization problem of substitutable products with fixed reusable capacities. At any time, a potential user with her preference model (possibly adversarially chosen) arrives to the selling platform and the platform offers a subset of products from the available set of products to the user. The user selects a product with probability given by her preference model, uses it for a random duration, which is distributed according to a distribution that only depends on the product selected, and generates revenue to the seller. The revenue contribution depends on the product selected and the actual usage time of this user. The goal of the seller is to find a policy for determining the assortment offered to each arrival to maximize the expected cumulative revenue over a time horizon. We find that a simple myopic policy offering the available assortment that maximizes the expected revenue from a single user at her arrival time provides a good approximation for the problem. In particular, we show that the myopic policy is $1/2$-competitive, i.e., the expected cumulative revenue of the myopic policy is at least $1/2$ times the expected cumulative revenue of an optimal clairvoyant policy that has full information about the adversarially chosen user sequence, including their preference models and arrival epochs. The proof is based on partitioning the expected revenue of optimal clairvoyant policy into two parts and a coupling argument that allows us to bound the two parts in terms of the expected revenue of the myopic policy. In Chapter 3, we study the surge pricing problem on a ride sharing platform when there is a demand shock to the traffic network. The goal of the platform is to maximize the revenue by setting the prices over the network and the assignments between drivers and riders. In particular, we model the city as a continuous two dimensional network with exogenous arrivals of baseline riders, available drivers and demand shocks. We consider the demand shock only exists in a short time scale, so the rider chooses to request the ride or not depending on their willingness to pay and the price quoted to them, and the driver accepts any price to provide service. Since drivers can see the price distribution on driver app, they only accept the assignment from the locations that are incentive compatible for them. Thus, the price change at one location may affect the operations over the network and the platform must consider the incentive of drivers when assigning them. We develop a model for this surge pricing problem and show the structural properties of an optimal solution. Once the prices at the location with demand shock is determined, we can determine the optimal prices on other part of the network. Then, the optimal assignments between riders and drivers can be determined analytically. The surge pricing problem reduces to one that only depends on the price at the location with demand shock. We then extend our model by including strategic behavior of riders, using throughput as objective, dealing with multiple demand shocks, un-constraining the price and considering movement time. We also conduct numerical experiments to study the properties of the model which can not be explored analytically. In Chapter 4, we study the demand response problem of computing price rebates to offer to the customers to reduce the consumption in the presence of power flow constraints and transmission losses on the distribution grid. In particular, we employ alternating current power flow model for the power flow constraints with transmission loss. However, the demand response problem with alternating current power flow constraints is known as a non-convex problem, which is in-tractable to solve. To overcome this, we apply a semi-definite relaxation of alternating current power flow model to obtain a convex approximation for the problem. At the same time, to handle the uncertainty in the power reduction of customers, we use sample average to approach the expected cost and linear injection approximation to estimate the impact of uncertainty in the power reduction. Based on these relaxations and approximations, we propose an efficient iterative heuristic to solve the near-optimal offer price under alternating current power flow constraints and transmission losses. We conduct a substantial amount of numerical tests on our heuristic and compare its performance with other popular models. The result shows that our iterative heuristic leads to a significant reduction in the rebates that one needs to offer to shed a certain demand than the solution which does not consider full transmission loss in its model.

The thesis addresses the research question of how and why ‘prosuming' solar electricity evolves over time among social housing tenants with prepayment electricity meters. Prosuming is defined here as deliberately and simultaneously producing and consuming electricity. Using a Social Practice Theory framework, but also drawing on Time Geography, the thesis analyses prosuming as a ‘project'. This sees practitioners actively mobilising elements (meanings, skills and materials), as well as orchestrating everyday practices (i.e. laundering) and projects (i.e. 'Feeding-the-Meter') to the fulfilment of the 'Prosuming Project'. The overarching research question is ‘How and why does prosuming evolve for social housing tenants?' It is broken down into four subsidiary questions that firstly explore the period before solar panels, and then the three stages of the conceptual framework – adopting, establishing and committing to the Prosuming Project. The first question addresses how householders use electricity prior to the installation of solar panels and the role of two dominant, institutional projects: 'Feeding-the-Meter' and 'Maintaining-Family-Routines'. The second examines the features of households adopting the Prosuming Project and the need to mobilise a set of elements from within a disadvantaged community. The third question explores how the establishing phase is marked by a complex relationship between prosuming as a secondary, voluntary project, and dominant, institutional projects. This is further complicated by the role of synchronicity, finances and the changing seasons. The final subsidiary question addresses how a new vocabulary of elements emerged as practitioners committed to the Prosuming Project. It also explores how a transformative process took place both for practitioner and the project itself. In particular it highlights the potential in the future for an Energy Shifting, Storing, Saving & Sharing Project that could support disadvantaged communities, if they are able to mobilise the elements they need to perform it. This case study adopts an in-depth qualitative methodology, using serial interviews with seven households over ten months. The interviewees live in an area that in 2010 was ranked as within the ten percent most deprived in England, according to English Indices of Deprivation (DCLG). The research explores their lived experiences of the Prosuming Project. The thesis focuses on UK social housing tenants, who appear not to have been researched before for a prosuming-focused, social practice study. This enables the research to contribute to topical debates about future sustainability ‘winners and losers'. It also offers methodological insights into undertaking a social practice case study that explored lived experiences within a disadvantaged community. The research provides insights into how prosuming solar power is embedded in everyday life: how it can be supported or challenged by dominant projects, and how householders may develop new skills, understandings, and ways of using materials as their performances evolve.

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CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / This work proposes a methodology for feasibility study of the distribution of natural gas to remote areas without access through a backbone pipeline. In recent years, one can observe a strong increase in the participation of natural gas as input in energy supply all around the world, including Brazil. The State of CearÃ, in the Northeastern Brazil, shows nowadays a natural gas supply superavit of about four million cubic meters per day. Present natural gas distribution in Cearà State occurs only in Fortaleza Metropolitan area. Although there are in the State many important urban development poles with significant potential to consume natural gas they cannot count yet with necessary supply equipments of that power input as gas pipeline. This is an important problem because wood fuel is largely used in the countryside notwithstanding its damage to the environment. All over the world the attendance of secondary markets with natural gas has been supported by trucks or trains lines as a first step before implementing a pipeline. This work aims to propose and apply a methodology to find the economic and logistics feasibility to distribute natural gas to remote regions. Such a methodology makes use of discrete choice demand forecasting technique using both revealed and stated preference data as well as the capacity facility location problem modelling and conventional indicators of economic feasibility. A case study is discussed involving the CRAJUBAR region of Cearà State. The work aims to contribute in identification of scenarios in which one can have feasible situations of energy input substitution. / Esta dissertaÃÃo propÃe uma metodologia para estudo de viabilidade da distribuiÃÃo secundÃria de gÃs natural em regiÃes afastadas de redes primÃrias de gasodutos. Diante da seguranÃa de fornecimento do gÃs natural apresentada atualmente no paÃs e no Mundo, a sua participaÃÃo na matriz energÃtica vem se intensificando nos Ãltimos anos. O Estado do Cearà apresenta superavit na oferta equivalente a quatro milhÃes de metros cÃbicos por dia de gÃs. Atualmente, a distribuiÃÃo do gÃs natural, nesse Estado, à realizada apenas na RegiÃo Metropolitana de Fortaleza, sendo que no interior se encontram importantes polos de desenvolvimento, como a RegiÃo do CRAJUBAR com uma base industrial com potencial de consumo de gÃs natural, que poderia levar à substituiÃÃo do uso principalmente de lenha no processo produtivo das empresas e, tambÃm, poderia propiciar a interiorizaÃÃo do uso do energÃtico em regiÃes ainda nÃo atendida por gasodutos. O atendimento aos consumidores de gÃs natural tem ocorrido por meio da utilizaÃÃo de distribuiÃÃo secundÃria (gasoduto virtual) indutora de mercado. Assim o objetivo deste estudo reside em propor e aplicar uma metodologia de determinaÃÃo da viabilidade da distribuiÃÃo secundÃria do gÃs natural para regiÃes nÃo atendidas por gasodutos, instrumentada pelo uso de tÃcnicas de previsÃo de demanda, de otimizaÃÃo de custos e de planilha eletrÃnica na determinaÃÃo da viabilidade econÃmica. O trabalho busca contribuir na identificaÃÃo de cenÃrios viÃveis de substituiÃÃo energÃtica para o uso do gÃs natural na regiÃo em estudo.