We evaluate the external effects of 183 large mergers at the market level by assessing the impact on the main competitors of the merging firms. Using synthetic control groups and difference in difference estimation, we find that the return on assets of rival firms increases significantly after a merger. The size of the effect varies strongly with market characteristics and the intensity of competition.

Yes / New healthcare models are being explored to enhance care coordination, efficiency, and outcomes. Evidence is scarce regarding the impact of vertical integration of primary and secondary care on emergency department (ED) attendances, unplanned hospital admissions, and readmissions. Aim To examine the impact of vertical integration of an NHS provider hospital and 10 general practices on unplanned hospital care Design and setting A retrospective database study using synthetic controls of an NHS hospital in Wolverhampton integrated with 10 general practices, providing primary medical services for 67 402 registered patients. Method For each vertical integration GP practice, a synthetic counterpart was constructed. The difference in rate of ED attendances, unplanned hospital admissions, and unplanned hospital readmissions was compared, and pooled across vertical integration practices versus synthetic control practices pre-intervention versus post-intervention. Results Across the 10 practices, pooled rates of ED attendances did not change significantly after vertical integration. However, there were statistically significant reductions in the rates of unplanned hospital admissions (−0.11, 95% CI = −0.18 to −0.045, P = 0.0012) and unplanned hospital readmissions (−0.021, 95% CI = −0.037 to −0.0049, P = 0.012), per 100 patients per month. These effect sizes represent 888 avoided unplanned hospital admissions and 168 readmissions for a population of 67 402 patients per annum. Utilising NHS reference costs, the estimated savings from the reductions in unplanned care are ∼£1.7 million. Conclusion Vertical integration was associated with a reduction in the rate of unplanned hospital admissions and readmissions in this study. Further work is required to understand the mechanisms involved in this complex intervention, to assess the generalisability of these findings, and to determine the impact on patient satisfaction, health outcomes, and GP workload.

In this dissertation, I study econometric issues in network and health economics. Measurement error is a ubiquitous problem in the peer effects literature that is not well understood. In Chapter 1, ``Measurement error in peer effects,'' I develop a constructive approach to empirically assess the bias caused by links missing at random. I apply my method to study the bias in peer effect estimates of recreational and physical activities among adolescents in the United States. I find that the magnitude and direction of the bias depends on the estimator. Estimators that measure the aggregate effect of peers' outcomes are more robust to measurement error and can be unbiased even when fifty percent of peer interactions are unobserved. Estimators that measure the average effect of peers'’ outcomes are more susceptible to measurement error and suffer from a persistent downward bias. My findings illustrate the importance of understanding measurement error's impact, when measurement error will likely bias results and when it can be safely ignored. In Chapter 2, ``Non-random errors in peer effects,'' I study the effects of measurement error on a generalized peer effect model that nests two of the most commonly used estimators. Measurement error in the specification of peer groups leads to biased estimates. I adapt Monte Carlo methods developed for studying measurement error when peers' interactions are missing at random to understand the effects of top-coding, non-random errors and spurious peer interactions. I find that non-random errors pose the greatest threat, often leading to overestimation and persistent biases. Top-coding can also severely bias estimates when the constraint impacts a majority of individuals but otherwise has a mild effect. While spurious links in limited quantities can often be ignored. Chapter 3, ``Nurse outreach and frequent emergency department users: A synthetic control analysis,'' studies the effects of an intervention to promote primary care engagement among frequent emergency department users. Emergency departments are one of the costliest places to receive care and are routinely overcrowded. Various policy initiatives have yielded mixed findings. I use synthetic control methods to analyze the effects of a nurse outreach program for frequent emergency department users implemented by a major U.S. insurer. The program seeks to reduce emergency department utilization by promoting primary care engagement. I leverage a unique commercial claims data set to measure the effects of the program on primary care and emergency department utilization. My findings suggest that six months after treatment nurse outreach increased primary care utilization by 15 percent; however, I find no clear effect on emergency department utilization. My findings indicate that increasing primary care engagement may not be sufficient to prevent emergency department over utilization. / Economics

This thesis investigates the effects football games in major international tournaments have on stock market returns. The major international football tournaments are limited to the FIFA World Cup and the UEFA European Championship, and the games studied are only the finals of these tournaments. The thesis deploys a method of difference in difference with synthetic control groups to capture any effects winning or losing of these games may have on the stock market returns in the following days. The last 22 years of finals in the FIFA World Cup and UEFA European Championship are studied in 11 games and thus 22 treatments. In general, a good fit of the synthetic counterfactuals prior to the event taking place is achieved. The positive and negative events are looked at separately rather than game by game since the distinction between negative and positive events is made by previous literature. All games are treated as equally important since they are all the final of a tournament. The estimated gaps are insignificant for a majority of the games, and no causal relationship between the outcome of finals in international football tournaments and returns on broad stock market indices can be established, possible reasons for this are, among other things, that the indices used in this study is mainly all share indices and large cap indices, which are generally stable.

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Submitted by Eduardo Cytrynowicz (educytry@gmail.com) on 2017-08-28T17:10:31Z No. of bitstreams: 1 diss_mestrado-ecytrynowicz-vfinal.pdf: 806898 bytes, checksum: 3d3b1685fc0da356141308510cfa7cf6 (MD5) / Rejected by Joana Martorini (joana.martorini@fgv.br), reason: Prezado Eduardo, boa tarde. O arquivo foi rejeitado por não estar de acordo com as Normas. Segue abaixo o link com todos os requisitos necessários para aprovação do seu trabalho. http://sistema.bibliotecas-sp.fgv.br/sites/bibliotecas.fgv.br/files/bibnormas1.pdf Qualquer dúvida, entre em contato no e-mail: mestradoprofissional@fgv.br ou ligue: 3799-7764 Att. on 2017-08-28T18:05:10Z (GMT) / Submitted by Eduardo Cytrynowicz (educytry@gmail.com) on 2017-08-28T18:24:43Z No. of bitstreams: 1 diss_mestrado-ecytrynowicz-vfinal.pdf: 806514 bytes, checksum: c54ae67e5045ab12bc44ed55deacd0ed (MD5) / Rejected by Joana Martorini (joana.martorini@fgv.br), reason: . on 2017-08-28T18:46:48Z (GMT) / Submitted by Eduardo Cytrynowicz (educytry@gmail.com) on 2017-08-28T18:55:45Z No. of bitstreams: 1 diss_mestrado-ecytrynowicz-vfinal.pdf: 806482 bytes, checksum: b340baf6ad3e6a4483e58bb92c55448e (MD5) / Approved for entry into archive by Joana Martorini (joana.martorini@fgv.br) on 2017-08-28T19:04:22Z (GMT) No. of bitstreams: 1 diss_mestrado-ecytrynowicz-vfinal.pdf: 806482 bytes, checksum: b340baf6ad3e6a4483e58bb92c55448e (MD5) / Made available in DSpace on 2017-08-29T12:42:34Z (GMT). No. of bitstreams: 1 diss_mestrado-ecytrynowicz-vfinal.pdf: 806482 bytes, checksum: b340baf6ad3e6a4483e58bb92c55448e (MD5) Previous issue date: 2017-08-18 / Empregamos o método de controle sintético para realizar um estudo de caso visando avaliar se o encolhimento econômico do Brasil durante o governo da presidente Dilma Rousseff foi causado por fatores domésticos ou internacionais. O estudo comparou os resultados da economia brasileira ao longo de toda duração desse governo em comparação com o potencial crescimento para o país. Estimamos esse contrafactual através de dados de países não afetados pelas políticas locais. Os resultados empíricos sugerem que, caso a economia brasileira tivesse seguido as mesmas tendências dos demais países, provavelmente teria experimentado um crescimento sustentável, muito diferente do que realmente ocorreu. / We use the synthetic control method to perform a case study to understand if the economic shrinking of Brazil during the government of President Dilma Rousseff was caused by domestic or international factors. The study compared the outcomes of the Brazilian economy under the entire government as opposed to what would have been the potential outcomes defined through a counterfactual estimated through foreign countries, thus unaffected by the local policies. The empirical results suggest that was Brazil to follow the same trends that the rest of the countries experienced, it would probably have experienced a sustainable growth, much different from what has actually happened.