The rapid growth of online games enables firms to charge players for virtual goods they sell for use within their online game environments. Determining prices for such virtual goods is inherently challenging due to the absence of explicit supply curve as the marginal cost of producing additional virtual goods is negligible. Utilizing sales data, we study daily revenue of a firm operating a virtual world and selling cards. Explicitly, we analyze the impact of new product releases on revenue using ARIMA with intervention model. We show that during initial days after a new product release, the firm's daily revenue significantly increases. Using a quality measure, based on the Elo rating method, we can determine the relative good prices based on good usage. Applying this method we show that the rating of a product can be a good proxy for units sold. We conclude that our quality-based measure can be adopted for pricing other virtual goods.

The U.S. furniture industry has faced the challenge from increasing imports of furniture from foreign countries over the last decades. In the first part of this thesis, the import pattern of wooden bedroom furniture and the antidumping investigation against China were summarized, and furthermore, intervention analysis was employed to assess its impacts on the import value and unit price of China. The results revealed that the impact on import values was temporary but there was no significant impact on unit prices. The traditional suppliers have been substituted by the newly developing countries such as China and Vietnam. In the second part of this thesis, to explain the market structure change, a dynamic AIDS model was used to analyze the consumer behavior and evaluate the impacts of antidumping investigation on the major competitors in the second part. The results indicated that most imported wooden bedroom furniture can be substituted between suppliers and trade diversion occurred from China to Vietnam, Indonesia, and Brazil.

O objetivo geral desta tese, composta por três artigos, é analisar as causas da criminalidade. As análises são feitas sob a ótica da Economia do Crime. Os dois primeiros artigos são independentes, mas complementares. Neles se busca lançar luz sobre as possíveis causas da queda do crime na cidade São Paulo. A ênfase recai na política de desarmamento dos cidadãos, no desempenho da Polícia e nas condições econômicas, em particular do mercado de trabalho. No primeiro deles, o objetivo é avaliar o efeito do Estatuto do Desarmamento sobre a criminalidade letal. Para isso foram utilizados dados de séries temporais da cidade de São Paulo na aplicação de uma metodologia de análise de intervenção. A hipótese de que a política de desarmamento causou redução na taxa de crimes letais não é rejeitada. Partindo dessa evidência, no segundo artigo o principal objetivo é investigar possíveis causas da significativa redução da criminalidade na cidade de São Paulo. Por meio de uma análise de cointegração evidenciaram-se relações de longo prazo entre crime, atividade econômica e desempenho da Polícia. Os resultados indicam que a taxa de crimes letais é positivamente relacionada ao desemprego, negativamente relacionada ao salário real e negativamente relacionada aos resultados das atividades de polícia, especificamente prisões e apreensão de armas de fogo. Ademais, não é rejeitada a hipótese de que o Estatuto do Desarmamento causou redução na taxa de crimes letais, reforçando a conclusão feita no primeiro artigo desta tese. No terceiro artigo, o foco das análises passa a ser os determinantes do risco de vitimização criminal. O objetivo é investigar os efeitos da riqueza dos indivíduos no risco de serem vítimas de crimes contra a propriedade, em particular crimes de furto/roubo a residência e furto/roubo a pessoa. Em termos específicos, o intuito é investigar se a relação entre risco de vitimização e riqueza pode ser descrita por uma parábola com concavidade voltada para baixo. São utilizados os dados de duas pesquisas domiciliares de vitimização realizadas na cidade de São Paulo na estimação de modelos probit. Os resultados das estimações indicaram que a riqueza dos indivíduos é um dos determinantes do risco de vitimização criminal a propriedade. Ademais, evidenciou-se que o risco de vitimização cresce com a riqueza, mas atinge um ponto de máximo, a partir do qual se reduz para níveis de riqueza mais elevados. / This three-article PhD thesis aims to investigate the causes of crime using an economic approach. The first two articles are independent, but complementary. In these articles, the objective is to shed light on possible causes of reductions in the crime rate in Sao Paulo city, focusing on the citizen disarmament policy, police performance, economic conditions and, particularly, the labor market. In the first article, the objective is assessing the effect of the Disarmament Statute on lethal crime rates. For this purpose, we used time-series data for Sao Paulo city in applying an intervention analysis methodology. The hypothesis that the disarmament policy led to a decline in the lethal crime rate is not rejected. Based on this evidence, the main objective of the second article is to investigate possible causes for the significant reduction observed in crime rates in Sao Paulo city. By applying a cointegration analysis, we observed long-run relationships between crime, economic activity and police performance. The results indicate that the lethal crime rate is positively related to unemployment and negatively related to real wages and to the results of law-enforcement activities, specifically arrests and seizure of firearms. Moreover, the hypothesis that the Disarmament Statute led to a reduction in the lethal crime rate is not rejected, reinforcing the conclusion arrived at in the first article of this thesis. In the third article, the focus of the analysis shifts to the determinants of criminal victimization. In this study, the objective is to investigate the effects of the wealth of individuals on the risk of becoming victims of property crimes, particularly crimes of theft/robbery of residence and theft/robbery of person. Specifically, its aim is to investigate whether the relationship between wealth and victimization risk can be described by a concave down parabola. Data from two household surveys on victimization held in Sao Paulo were used to estimate probit models. It became evident that the wealth of individuals is one of the determinants of victimization risk. And it was found that criminal victimization risk increases with wealth, but that it reaches a maximum point from which it decreases as wealth levels increase.

Social media has created new protest spaces and has enabled people to do things differently. The focus of the research is on campaign groups, created before social media was used as a tool for protest. It has been undertaken to achieve the aim of the challenges and opportunities of incorporating new forms of social media into existing protest campaigns through a case study of anti-airport expansion groups in the UK. Social media data was obtained from three anti-airport expansion groups which included the extraction of approximately 9,000 tweets and 8,000 Facebook posts. The data were then analysed using social network analysis, time series analysis and semi-structured interviews. The results of social network analysis and time series analysis informed the development of the questions directed at the social media coordinators of each group. The main findings are that Airport Watch and HACAN Clearskies exhibit very similar Twitter networks and favour interaction with the media, similar anti-airport expansion groups and also pro-airport expansion groups. Transition Heathrow demonstrates more varied interaction patterns. All groups dominate their respective Facebook page and group networks apart from HACAN Clearskies which has non-assigned leaders controlling information dissemination in the group. Time series analysis uncovered variations in social media usage; overall for all three campaign groups Twitter was utilised more than Facebook.

O objetivo geral desta tese, composta por três artigos, é analisar as causas da criminalidade. As análises são feitas sob a ótica da Economia do Crime. Os dois primeiros artigos são independentes, mas complementares. Neles se busca lançar luz sobre as possíveis causas da queda do crime na cidade São Paulo. A ênfase recai na política de desarmamento dos cidadãos, no desempenho da Polícia e nas condições econômicas, em particular do mercado de trabalho. No primeiro deles, o objetivo é avaliar o efeito do Estatuto do Desarmamento sobre a criminalidade letal. Para isso foram utilizados dados de séries temporais da cidade de São Paulo na aplicação de uma metodologia de análise de intervenção. A hipótese de que a política de desarmamento causou redução na taxa de crimes letais não é rejeitada. Partindo dessa evidência, no segundo artigo o principal objetivo é investigar possíveis causas da significativa redução da criminalidade na cidade de São Paulo. Por meio de uma análise de cointegração evidenciaram-se relações de longo prazo entre crime, atividade econômica e desempenho da Polícia. Os resultados indicam que a taxa de crimes letais é positivamente relacionada ao desemprego, negativamente relacionada ao salário real e negativamente relacionada aos resultados das atividades de polícia, especificamente prisões e apreensão de armas de fogo. Ademais, não é rejeitada a hipótese de que o Estatuto do Desarmamento causou redução na taxa de crimes letais, reforçando a conclusão feita no primeiro artigo desta tese. No terceiro artigo, o foco das análises passa a ser os determinantes do risco de vitimização criminal. O objetivo é investigar os efeitos da riqueza dos indivíduos no risco de serem vítimas de crimes contra a propriedade, em particular crimes de furto/roubo a residência e furto/roubo a pessoa. Em termos específicos, o intuito é investigar se a relação entre risco de vitimização e riqueza pode ser descrita por uma parábola com concavidade voltada para baixo. São utilizados os dados de duas pesquisas domiciliares de vitimização realizadas na cidade de São Paulo na estimação de modelos probit. Os resultados das estimações indicaram que a riqueza dos indivíduos é um dos determinantes do risco de vitimização criminal a propriedade. Ademais, evidenciou-se que o risco de vitimização cresce com a riqueza, mas atinge um ponto de máximo, a partir do qual se reduz para níveis de riqueza mais elevados. / This three-article PhD thesis aims to investigate the causes of crime using an economic approach. The first two articles are independent, but complementary. In these articles, the objective is to shed light on possible causes of reductions in the crime rate in Sao Paulo city, focusing on the citizen disarmament policy, police performance, economic conditions and, particularly, the labor market. In the first article, the objective is assessing the effect of the Disarmament Statute on lethal crime rates. For this purpose, we used time-series data for Sao Paulo city in applying an intervention analysis methodology. The hypothesis that the disarmament policy led to a decline in the lethal crime rate is not rejected. Based on this evidence, the main objective of the second article is to investigate possible causes for the significant reduction observed in crime rates in Sao Paulo city. By applying a cointegration analysis, we observed long-run relationships between crime, economic activity and police performance. The results indicate that the lethal crime rate is positively related to unemployment and negatively related to real wages and to the results of law-enforcement activities, specifically arrests and seizure of firearms. Moreover, the hypothesis that the Disarmament Statute led to a reduction in the lethal crime rate is not rejected, reinforcing the conclusion arrived at in the first article of this thesis. In the third article, the focus of the analysis shifts to the determinants of criminal victimization. In this study, the objective is to investigate the effects of the wealth of individuals on the risk of becoming victims of property crimes, particularly crimes of theft/robbery of residence and theft/robbery of person. Specifically, its aim is to investigate whether the relationship between wealth and victimization risk can be described by a concave down parabola. Data from two household surveys on victimization held in Sao Paulo were used to estimate probit models. It became evident that the wealth of individuals is one of the determinants of victimization risk. And it was found that criminal victimization risk increases with wealth, but that it reaches a maximum point from which it decreases as wealth levels increase.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This research aims to evaluate the performance of time-series models together with the use of analysis, when the time for action is determined by visual inspection of the series or the spectral analysis, greenhouse gas emission data. In carrying out this research were considered data from the time series of the measurement of ozone gas (O3), nitrogen dioxide (NO2), carbon monoxide (CO) and sulfur dioxide (SO2), understood in January 1986 to December 2014, referring to the first day of each month, totaling 348 observations. The models were performed pre-analysis, using spectral analysis to determine the period in which the intervention must be done, show better performance considering the AIC and BIC criteria. Indicating that whenever possible to use this tool as an aid for modeling time series who need intervention. / Esta pesquisa tem como objetivo avaliar o desempenho dos modelos de séries temporais conjuntamente com a análise de intervenção, quando o instante de intervenção é determinado pela inspeção visual da série ou pela análise espectral em dados de emissão de gases poluentes. Para a execução desta pesquisa foram considerados os dados da série histórica da medição dos gases ozônio (O3), dióxido de nitrogênio (NO2), monóxido de carbono (CO) e dióxido de enxofre (SO2), compreendidos no período de janeiro de 1986 a dezembro de 2014, referente ao primeiro dia de cada mês, totalizando 348 observações. Os modelos em que realizou-se a pré-análise, utilizando-se da análise espectral, para determinar o período em que análise de intervenção foi realizada, apresentou melhor desempenho considerando-se os critérios AIC e BIC, indicando sempre que possível utilizar essa ferramenta como auxiliar para modelagem de séries temporais.

The Objective of this thesis is to address some interesting problems in the Indian cellular services market. The first problem we address relates to identifying important change points that marked the evolution of the telecom market since Indian Independence. We use the data on per-capita availability of telephones in India to this effect. We identify important change points that mapped to the computerization move in 1989, the liberalization and globalization policies starting from 1991 and subsequently the introduction of NTP 1997 and NTP 1999. We also identify the important change points that mark the growth of cellular services subscriber base in India. We map change points detected to some of the important macro level policy initiatives that were taken by TRAI. The second problem we address is the assessment of policy interventions on the growth of cellular subscriber base in India. We model the impact of two important policy interventions namely, the NTP 1999 and its spill-over policy the entry of the fourth player into the market to offer services. We model the abrupt temporary, abrupt permanent and gradual permanent impacts of these interventions individually and in a coupled manner. We are arguably the first to use the intervention analysis and change point analysis to study the Indian telecom market. The third problem relates to the most challenging task of forecasting the growth of cellular services subscribers in India. We use novel machine learning techniques like ε-SVR and ν-SVR and compare its performance with ANN and ARIMA using standard performance metrics. Initially, we venture to predict the aggregate subscriber growth of cellular mobile subscribers in India using the SVR techniques. This would be of interest to the policy makers from a strategic standpoint. Subsequently, we predict the marginal(monthly) subscriber growth using SVR and tabulate the results for varying depths of forecasting which would be of interest to service providers form an operation standpoint. We find that the SVR techniques performed better than ANN and ARIMA particularly with respect to forward or out-sample forecasting when the time periods increase. The final problem involves a differential game model in an oligopoly set up for the telecom service providers who tried to optimize their advertisement innovation mix in order to maximize their discounted flow of profits. We consider the situation where the service providers make Cournot conjectures about the action of their rivals. The firms would not enter into agreements or form cartels. The firms choose the quantity they want to sell simultaneously. The essence of the Cournot conjecture was that though it was a quantity based competition, no single firm could unilaterally try to improve the total quantity sold in the market. Every firm made only one decision and did so when other firms were simultaneously making decisions. We have come across papers that considered either advertisement or product/process innovation separately but not together. We incorporate both these control variables with the inverse demand function as the state variable. We propose an open-loop solution that is dependent on time. We conduct experiments with various combinations of churn and spill-over rates of advertisement and innovation and thereby get some managerial insights.

The aim of this study is to analyze whether creating an own category for Socially Responsible Investment Funds (FISR) in Brazil generates time series changes in heritage and cash flow of these funds. We studied all FISR Brazilians during the period 2001 to 2009. The methodology used was the Box & Jenkins (1970) and interventions. The results reveal interventions in the two variables; however, the interventions take place before the change of category. Another important conclusion is that the category change does not cause alterations in the time series of the two variables considered. / El objetivo de este estudio es analizar si la creación de una categoría propia para los Fondos de Inversión Socialmente Responsables (FISR) de Brasil generó cambios en las series temporales de patrimonio y flujo de dinero de estos fondos. Para ello se han analizado todos los FISR brasileños existentes durante el periodo comprendido entre los años 2001 y 2009, aplicando las metodologías de Box y Jenkins (1970) y de intervenciones. Los resultados revelan intervenciones en las dos variables, sin embargo las intervenciones tuvieron lugar antes del cambio de categoría. Otra importante conclusión es que el cambio de categoría no provocó alteraciones en las series temporales de las dos variables consideradas.

本文使用 1981 年 1 月 5 日至 1997 年 5 月 31 日台灣加權股價指數以及交易股數的資料探討台灣股市的時間序列特性，並且針對政府對股市的干預政策檢定政策干預的有效性。本文採用的實證方法包含 Augmented Dickey-Fuller(ADF)單根檢定，Perron 結構性改變檢定， ARCH 效果檢定，干預分析(Intervention Analysis)以及 Granger 因果關係檢定。實證檢定的結果如下： 1、在單根檢定方面，股價指數、交易股數和股價指數變異數三個時間序列都是一階穩定序列。 2、在 Parron 結構性改變檢定方面，股價指數、交易股數和股價指數變異數三個時間序列在 1990 年 5 月到 10 月之間曾經發生明顯的結構性改變。 3、在 ARCH 效果檢定方面，股價指數和交易股數二個時間序列的殘差項都有 ARCH(1)效果存在，而股價指數變異數的殘差項不存在 ARCH(1)效果。 4、在干預分析方面，穩定基金對股價指數的干預效果不顯著。 在漲跌幅限制方面，漲跌幅限制的變動對股價指數、交易股數及股價指數變異數的干預效果都不明顯。 在證卷交易稅稅率改變的干預分析方面，證卷交易稅稅率改變對交易股數和股價指數變異數沒有影響，但是證交稅稅率變動和股價指數呈現正向的關係。 5、在 Granger 因果關係檢定方面，本研究發現漲跌幅限制改變和股價指數漲跌二者互為因果，但是股價指數對漲跌幅的影響較大。 在證卷交易稅稅率改變與股市的因果關係方面，本研究發現股價指數的漲跌是證交稅稅率改變之因，顯示主管機關的證交稅稅率政策是受股市的市場狀況所左右。 / In this paper, I examine the effectiveness of official intervention in Taiwan's equity market. I consider the security transaction tax, price limit and stabilization funds as examples. The nonstationarity and structural changes of equity index time-series process were first detected and detrended. The Autoregressive Conditional Heteroskedasticity (ARCH) model is employed to examine the intervention effectiveness, since it allows for a formal test of changes in the index mean level, index conditional variance or both, in response to the changes of security transaction tax and price limit. The results implies that policy authority adjusted security transaction tax and price limit in accordance to the change of equity index level. I also find that the imposition of security transaction tax and price limit have no significant effect on reducing the equity index volatility.

近年來國際金融局勢詭譎多變，金融危機層出不窮，無論外資或有意投入國外股市的投資人都勢必更加小心。本研究乃針對亞太盆地國家的股票報酬率與國家信用水準變動做分析，並依開發中國家與已開發國家之別，嘗試探究其差異。本文的研究方法採用時間序列的模型(干預模型與衝擊反應分析)，檢定亞太盆地國家股票報酬率的時間序列型態，及國家信用變動對股票報酬率及其波動性的影響。實證結果顯示： 1.無論開發中國家或已開發國家，其股票報酬率並不受自身股票報酬率的波動度影響，此結論恰與Baillie and Degennaro(1990)吻合。 2.國家信用水準變動對股票報酬率的影響未落後達一個月之久。 3.國家信用變動對已開發國家的股票報酬率及其波動度不具顯著的解釋力。 4.國家信用改變對開發中國家股票報酬率及其波動度較具解釋力，但影響方向不一致，原因可能是開發中國家的投資障礙較多。 5.衝擊反應分析受限於開發中國家股市資料較少及國家信用分數型態，而未有一致而明顯的結論。 第一章、 緒論••••••••••••••••••••••••1 第一節 研究背景與動機••••••••••••••••••••1 第二節 研究目的•••••••••••••••••••••••4 第三節 研究限制•••••••••••••••••••••••4 第四節 研究內容與研究架構••••••••••••••••••5 第二章、 文獻探討••••••••••••••••••••••7 第一節 股票波動度的相關文獻•••••••••••••••••7 第二節 國家風險的相關文獻••••••••••••••••••8 第三節 干預分析的相關文獻••••••••••••••••••10 第四節 衝擊反應分析的相關文獻••••••••••••••••12 第三章、 資料來源與說明•••••••••••••••••••13 第一節 太平洋盆地國家的股市資料來源與類型••••••••••13 第二節 敘述統計•••••••••••••••••••••••15 第三節 使用Institutional Investor的國家信用評等指標為解釋變數之因•22 第四節 國家信用風險評比決定因子與過程••••••••••••24 第五節 國家風險指標的有效性•••••••••••••••••25 第四章、 實證結果••••••••••••••••••••••26 第一節 理論架構•••••••••••••••••••••••26 第二節 檢驗各國股價報酬的時間序列型態••••••••••••29 第三節 變異數自身相關檢定(ARCH、GARCH檢定)••••••••38 第四節 波動度解釋力檢定•••••••••••••••••••45 第五節 國家信用評等解釋力檢定••••••••••••••••48 第六節 衝擊反應分析•••••••••••••••••••••59 第五章、 結論與後續研究建議•••••••••••••••••74 第一節 結論•••••••••••••••••••••••••74 第二節 後續研究建議•••••••••••••••••••••76 參考文獻•••••••••••••••••••••••••••77 一、 中文部份••••••••••••••••••••••••77 二、 英文部份••••••••••••••••••••••••77 附錄(外國專業投資機構直接投資國內狀況分析表) •••••••••80 / For the recent years, the global financial environment has been changing rapidly, which reminds qualified foreign institutional investors of more caution. This survey focuses on the relationship between stock returns, volatility and country credit rating changes among countries in the Asia-Pacific Basin. This research further divides the 12 sample countries into two categories, developed markets and emerging ones, and finds out the differences between both groups. The empirical methods used here are intervention analysis and impulse response analysis. The empirical results are as follows: 1. The stock return and its volatility do not have statistically significant relation in both developed markets and emerging ones, which coincides with the conclusion by Baillie and Degennaro(1990). 2. The impact of changes in country credit level on stock returns will work within one month; that is to say, changes in country credit level this month will affect stock returns of the current month. 3. Country credit change has no impact on stock returns of the developed markets. 4. Changes in country credit levels of the emerging markets have apparent influence on their stock returns but no identical signs. This may result from the common barriers existed in the emerging markets for foreign investors. 5. The impulse response analysis doesn't have an apparent and agreeable result owing to the constraint of rare data.