<p><strong><p><strong>Purpose: </strong></p><p><em>Our main purpose is to explore, describe and analyze the organizational conduct when implementing automated trading systems (ATS) in companies, investigate the organizational challenges arising from this, and the effects these have on a successful diffusion</em>. As the extent of implementing ATS in the Swedish financial industry has not been explored to any greater extent, it is therefore also imperative to explore this; which will be seen as a secondary purpose to this article.<strong></strong></p><p><strong>Background: </strong></p><p>The study is based on innovation and diffusion theories, as well as those of power structures and organization. Further, an explanation of ATS and its dynamics is provided and discussed to facilitate a definition of the term.</p><p><strong>Method: </strong></p><p>The research has been carried out as an exploratory, descriptive and analytical qualitative study.<strong> </strong>We have conducted case studies of 7 companies that are implementing, or evaluating the implementation, of ATS. The data was collected through interviews.</p><p><strong>Conclusion: </strong></p><p>The majority of the case companies are in the clarifying and routinizing stages of the innovation process. What is found unique with ATS is that it can be implemented partly. The dimensions found central to a smooth diffusion in the companies are the <em>required level of competence-sharing</em> and <em>complexity of implementation.</em></p></strong></p>

本篇論文主要探討台灣期貨市場於2005年至2008年的快速抽單(Fleeting orders)現象。文章將市場交易者區分為機構法人、散戶、自營商以及外資共四類族群，研究抽單背後的動機是否與各族群中交易者的下單積極程度、追價動作，或是降低成交成本有關。實證結果顯示，機構法人在快速抽單動作上無顯著動機；在散戶部分，僅部分散戶具有能力進行快速抽單，而其主要動機是為了降低交易成本。自營商的進場動機，主要是以造市為考量，因此測試市場上是否存在更激進的交易對手單是快速抽單的原因之一。此外，自營商亦會因要降低成交成本而進行快速抽單的動作。由於外資的主要策略是使用波段操作獲取大額利潤，無顯著證據證明外資進行快速抽單的動機是涵蓋於上述三種假設。 本文亦透過實證分析，探討快速抽單與合約報酬的關係，並以研究觀察有較高的快速抽單率是否會帶來較佳報酬，實證結果顯示各族群皆無顯著正相關，但散戶有顯著負相關。四類族群各自有不同的交易型態，故不能將他們概一而論，本篇論文的貢獻即是透過快速抽單，證明四個交易族群在程式交易上，具有不同的策略方向以及對於市場有不同的熟悉程度。 / This paper focuses on the phenomenon of fleeting orders in Taiwan’s futures markets from 2005 to 2008. Traders who in the markets will be divided into local institutional investors, individual, Dealer, and foreign institutional investors. Our study will find the motivation behind fleeting orders under the three hypotheses: attractive, chasing, and the cost-of-immediacy. The empirical results show that local institutional investors have no significant motivation. Only part of individual investors have the ability to use fleeting orders, and their main motivation is to reduce transaction costs. Dealers act as a market maker, so the main motivation for dealers is to raise liquidity. So to test whether a more aggressive limit orders exists in the market is one of the reasons for them to submit fleeting orders. In addition, dealers will also cancel limit orders in order to reduce the transaction costs. Because the main strategy for foreign institutional investors is to obtain a large profit during a period, they have no significant evidence to explain any motivation under the three assumptions. This article also analysis the relationship between fleeting orders and performance, and investigate whether the high fleeting ratio could bring much better profits. The empirical result show that all of four type investors have no significant positive correlation of fleeting orders and performance, but individual investors have significant negative correlation of fleeting orders and performance. Each of four type investors has different trading patterns, so that we should treat them case by case. The contribution of this paper is to prove that the four type investors have different strategies when they use trading program, and they also have different experience in Taiwan’s futures markets.

Submitted by PAULO SÉRGIO COELHO VIEIRA (coelhovieira.paulo@gmail.com) on 2015-04-15T23:04:53Z No. of bitstreams: 1 Paulo Vieira-HFT Industry_final_v1.pdf: 1540808 bytes, checksum: 1a0ee5cd10f415e74d56beb3e4b6f6c9 (MD5) / Rejected by Ana Luiza Holme (ana.holme@fgv.br), reason: Prezado Paulo, Todas as informações da contra capa e folha de aprovação devem ser em português pois a instituição é no Brasil. falta o agradecimento em português e inglês que deve ser depois da dedicatória a dedicatória deve ser em uma única folha em português e inglês e deve ser antes do agradecimento e depois da folha de aprovação e no fim da pagina a direita. no sumário não se coloca por exemplo a pagina da dedicatória, só deve aparecer a partir da introdução. as paginas só são numeradas a partir da introdução mas conta a partir da capa, exemplo introdução e a pagina 10, só aparecerá no trabalho em introdução a pagina 10 não pode ser numeral romano, deve ser numero exemplo 10. Ana Luiza Holme 3799-7760 on 2015-04-16T13:07:33Z (GMT) / Submitted by PAULO SÉRGIO COELHO VIEIRA (coelhovieira.paulo@gmail.com) on 2015-04-17T00:12:53Z No. of bitstreams: 1 Paulo Vieira-HFT Industry_final_v2.pdf: 1539919 bytes, checksum: e6fff3edaed078ed606a551c2ea0bf50 (MD5) / Approved for entry into archive by Ana Luiza Holme (ana.holme@fgv.br) on 2015-04-17T12:19:38Z (GMT) No. of bitstreams: 1 Paulo Vieira-HFT Industry_final_v2.pdf: 1539919 bytes, checksum: e6fff3edaed078ed606a551c2ea0bf50 (MD5) / Made available in DSpace on 2015-04-17T12:37:49Z (GMT). No. of bitstreams: 1 Paulo Vieira-HFT Industry_final_v2.pdf: 1539919 bytes, checksum: e6fff3edaed078ed606a551c2ea0bf50 (MD5) Previous issue date: 2015 / U. S. Equity Trading Industry has evolved quickly over the last decade. The U.S. equity market became an open architecture in which entrants with innovative technology can compete effectively. Several regulatory changes and technological innovations have enabled profound changes in market structure. These changes, along with improving high-speed technology, have acted as a catalyst, giving rise to a new approach to trading, named High Frequency Trading, hereafter referred as HFT. HFT Firms emerged and took over in large extent the market making business in providing liquidity. Although HFT has been growing massively, over the past four years, HFT firms have been far less profitable, since more firms entered the industry eroding the margins. Within this context, therefore, this thesis sought to provide a brief review of HFT business, followed by the analysis of its industry boundaries and the characteristics of the HFT environment. To this end, the thesis conducted an extensive literature review of previous research, qualitative public documents, such as, newspapers, meeting minutes and official reports. The thesis employed a series of frameworks, Entry Barriers and Mobility Barriers (Porter, 1980); Models of Industry Evolution (McGahan, 2004); Information-Intensive Industry Structure (Sampler, 1998), to analyze the boundaries of the HFT industry. Additionally, it employed Models of Industry Evolution (McGahan, 2004) and PESTEL (JOHNSON, SCHOLES, and WHITTINGTON, 2011) frameworks to analyze the industry and the environment surrounding HFT business. The analysis concluded that the firms employing HFT to compete in the Securities Trading industry compose an independent industry. / O Mercado Acionário Americano evoluiu rapidamente na última década. Este tornou-se uma arquitetura aberta em que participantes com tecnologia inovadora podem competir de forma eficaz. Várias mudanças regulatórias e inovações tecnológicas permitiram mudanças profundas na estrutura do mercado. Essas mudanças, junto com o desenvolvimento tecnológico de redes de alta velocidade, agiu como um catalisador, dando origem a uma nova forma de negociação, denominada Negociação em Alta Frequência (HFT). As empresas de HFT surgiram e se apropriaram em larga escala do negócio de formação de mercado, no fornecimento de liquidez. Embora HFT tem crescido massivamente, ao longo dos últimos quatro anos, HFT perdeu rentabilidade significativamente, uma vez que mais empresas aderiram ao setor reduzindo as margens. Portanto, diante deste contexto, esta tese buscou apresentar uma breve revisão sobre a atividade de HFT, seguida de uma análise dos limites deste setor, bem como, das características do macroambiente do HFT. Para tanto, a tese realizou uma extensa revisão do histórico literário, documentos públicos qualitativos, tais como, jornais, atas de reunião e relatórios oficiais. A tese empregou um ferramental de análise, Barreiras de Entrada e Mobilidade (Porter, 1980); Modelos de Evolução Setorial (McGahan, 2004); Estrutura do Setor de Informação Intensiva (Sampler, 1998), para analisar os limites do setor de HFT. Adicionalmente, empregou as ferramentas de análise, Modelos de Evolução Setorial (McGahan, 2004) e PESTEL (JOHNSON, SCHOLES, and WHITTINGTON, 2011), para analisar o setor e o contexto que envolve o negócio de HFT. A análise concluiu que as empresas que empregam HFT para atuar e competir no mercado acionário, compoem um setor independente.

Submitted by Isac Costa (isac.costa@gmail.com) on 2018-03-29T03:00:24Z No. of bitstreams: 1 COSTA, Isac. HFT - Compreender para Regular (2018).pdf: 2204316 bytes, checksum: 34d586d9b8bca337d4f2631f417e7c8d (MD5) / Rejected by Katia Menezes de Souza (katia.menezes@fgv.br), reason: Prezado Isac, Para que possamos aprovar seu trabalho são necessários alguns ajustes conforme norma ABNT/APA. ESTRUTURA: Capa (obrigatório) – No final da página a informação “2018” deverá constar abaixo da frase “São Paulo” e não ao lado como consta atualmente. Ficha catalográfica – Excluir a informação “presente trabalho foi realizado com apoio da Fundação Getúlio Vargas, Por meio da bolsa Mário Henrique Simonsen de Ensino e Pesquisa” Folha de aprovação- Não deverá conter a ata e sim um modelo anexo. Outra situação que detectamos é que no espaço de uma página para outra a algumas folhas em branco, favor exclui-las. Após os ajustes excluir o pdf já postado e submete-lo novamente para analise e aprovação. Qualquer dúvida estamos à disposição, Att. on 2018-04-02T20:20:05Z (GMT) / Submitted by Isac Costa (isac.costa@gmail.com) on 2018-04-03T11:41:00Z No. of bitstreams: 1 COSTA, Isac. HFT - Compreender para Regular (2018).pdf: 1858992 bytes, checksum: 4c53e5c7b819d28a0f2d41fdf22fdd62 (MD5) / Approved for entry into archive by Katia Menezes de Souza (katia.menezes@fgv.br) on 2018-04-03T12:03:00Z (GMT) No. of bitstreams: 1 COSTA, Isac. HFT - Compreender para Regular (2018).pdf: 1858992 bytes, checksum: 4c53e5c7b819d28a0f2d41fdf22fdd62 (MD5) / Approved for entry into archive by Suzane Guimarães (suzane.guimaraes@fgv.br) on 2018-04-03T12:21:35Z (GMT) No. of bitstreams: 1 COSTA, Isac. HFT - Compreender para Regular (2018).pdf: 1858992 bytes, checksum: 4c53e5c7b819d28a0f2d41fdf22fdd62 (MD5) / Made available in DSpace on 2018-04-03T12:21:35Z (GMT). No. of bitstreams: 1 COSTA, Isac. HFT - Compreender para Regular (2018).pdf: 1858992 bytes, checksum: 4c53e5c7b819d28a0f2d41fdf22fdd62 (MD5) Previous issue date: 2018-03-05 / High frequency trading (HFT) é uma técnica de negociação baseada em algoritmos que pode implementar estratégias variadas, das quais resultam um elevado número intradiário de mensagens enviadas aos sistemas de negociação das bolsas. High frequency traders (HFTs) são protagonistas no mercado secundário em termos de número de ofertas e negócios. Neste texto, procuramos definir os contornos deste já não tão novo fenômeno e os riscos a ele associados. Investigamos os objetivos pretendidos pela regulação, as regras aplicáveis e as dificuldades associadas a cada um delas. Assim, podemos avaliar se, no direito brasileiro, é necessário editar uma nova norma ou atualizar normas existentes e discutir qual poderia ser o seu conteúdo. A formulação de respostas regulatórias toma como ponto de partida os pressupostos teóricos do funcionamento do mercado de capitais, suas funções econômicas e o modo pelo qual o direito pode contribuir para que estas funções sejam desempenhadas adequadamente. Um estudo crítico dos HFTs nos permite examinar os riscos associados à sua atividade e à negociação algorítmica de um modo geral, bem como repensar o funcionamento do mercado, os objetivos da sua regulação e como estes podem ser alcançados. É imprescindível que seja realizado um esforço para a compreensão adequada de novas tecnologias que chegam ao mercado, avaliando seus riscos antes que seja disseminado um discurso de alarde ou medo. Este estudo também procura oferecer uma descrição atualizada do funcionamento do mercado secundário de capitais e como as tecnologias mais recentes influenciaram a dinâmica das negociações. / High frequency trading (HFT) is a kind of algorithmic trading which implements several strategies that result in a high number of intraday messages that are sent to exchanges and other trading venues. High frequency traders (HFTs) are key players in secondary markets given the number of orders and trades they generate. In this text, we explore the boundaries of this phenomenon and the associated risks. We investigate the regulation goals, the mechanisms to achieve such goals and the obstacles ahead. Then we evaluate whether it is necessary to create new rules or update the existing ones in Brazilian law – and what these new rules could be. The formulation of regulatory responses start with the analysis of a theoretical framework for the dynamics of capital markets, its economic functions and how Law can play a key part in this scenario. A critical study of HFTs enables us to assess its risks along with the risks of algorithmic trading in general, and, in addition, it is an invitation to rethinking how the market works, the goals that regulation can pursue and how they can be achieved. Understanding new technologies that emerge in capital markets is paramount before any risk assessment discussions in order to prevent hype and panic. This work also aims to provide an up to date description of the secondary market dynamics and how state-of-art trading technologies reshaped it.

The purpose of this thesis is: (i) to produce an in-depth data analysis and computer-based simulations of the market environment to investigate whether financial stability is affected by the presence of High-Frequency investors; (ii) to verify how High-Frequency Trading and financial stability interact with each other under non-linear conditions; (iii) whether non-illicit behaviours can still lead to potentially destabilising effects; (iv) to provide quantitative support to the theses, either from the audit trail data or resulting from simulations. Simulations are provided to test whether High-Frequency Trading: (a) has an impact on market volatility, (b) leads to market splitting into two tiers; (c) takes the lion's share of arbitrage opportunities. Audit trail data is analysed to verify some hypotheses on the dynamics of the Flash Crash. The simulation on the impact of High-Frequency Trading on market volatility confirms that when markets are under stress, High-Frequency Trading may cause volatility to significantly increase. However, as the number of ultra-fast participants increases, this phenomenon tends to disappear and volatility realigns to its standard values. The market tiering simulation suggests that High-Frequency traders have some tendency to deal with each other, and that causes Low-Frequency traders also to deal with other slow traders, albeit at a lesser extent. This is also a kind of market instability. High-Frequency Trading potentially allows a few fast traders to grab all the arbitrage-led profits, so falsifying the Efficient Market Hypothesis. This phenomenon may disappear as more High-Frequency traders enter the competition, leading to declining profits. Yet, the whole matter seems a dispute for abnormal gains only between few sub-second traders. All simulations have been carefully designed to provide robust results: the behaviours simulated have been drawn from existing literature and the simplifying assumptions have been kept to a minimum. This maximises the reliability of the results and minimizes the potential of bias. Finally, from the data analysis, the impact of High-Frequency Trading on the Flash Crash seems significant; other sudden crashes occurred since, and more can be expected over the next future. Overall, it can be concluded that High-Frequency Trading shows some controversial aspects impacting on financial stability. The results are at a certain extent confirmed by the audit trail data analysis, although only indirectly, since the details allowing the match between High-Frequency traders and their behaviour are confidential and not publicly available Nevertheless, the findings about HFT-induced volatility, market segmentation and sub-optimal market efficiency, albeit not definitive, suggest that careful monitoring by regulators and policy-makers might be required.

Submitted by Raphael Maaz (rfmaaz@gmail.com) on 2018-08-17T04:37:24Z No. of bitstreams: 1 Dissertation_20180817_RFM.pdf: 420668 bytes, checksum: 15c23fd991dfb5a7d5edff23f64e01b7 (MD5) / Rejected by Thais Oliveira (thais.oliveira@fgv.br), reason: Raphael, boa tarde! Para que possamos aprovar seu trabalho, a única alteração que deve ser feira é retirar o acento do "GETULIO" (nome da Escola). Por gentileza, alterar e submeter novamente. Qualquer dúvida, entre em contato. Thais Oliveira mestradoprofissional@fgv.br/ 3799-7764 on 2018-08-20T20:41:55Z (GMT) / Submitted by Raphael Maaz (rfmaaz@gmail.com) on 2018-08-21T03:59:50Z No. of bitstreams: 1 Dissertation_20180821_RFM.pdf: 420299 bytes, checksum: 16fbfa33cab672015314b8f39f931c77 (MD5) / Approved for entry into archive by Thais Oliveira (thais.oliveira@fgv.br) on 2018-08-21T23:50:47Z (GMT) No. of bitstreams: 1 Dissertation_20180821_RFM.pdf: 420299 bytes, checksum: 16fbfa33cab672015314b8f39f931c77 (MD5) / Approved for entry into archive by Suzane Guimarães (suzane.guimaraes@fgv.br) on 2018-08-22T13:12:56Z (GMT) No. of bitstreams: 1 Dissertation_20180821_RFM.pdf: 420299 bytes, checksum: 16fbfa33cab672015314b8f39f931c77 (MD5) / Made available in DSpace on 2018-08-22T13:12:56Z (GMT). No. of bitstreams: 1 Dissertation_20180821_RFM.pdf: 420299 bytes, checksum: 16fbfa33cab672015314b8f39f931c77 (MD5) Previous issue date: 2018-08-10 / O presente trabalho apresenta um estudo sobre catacterístitcas importantes da utilização de estratégias de negociações algorítmicas de alta frequência (HFT) por investidores que realizam operações com contratos futuros de taxa de câmbio em reais por dólar comercial no mercado brasileiro, tais como o nível de atividade de operadores que empregam este tipo de recurso e seus principais fatores de influência, a rentabilidade de participantes de instituições que adotam esta prática e a existência de padrões nas estratégias adotadas por negociadores algoritmicos. Dentre as conclusões obtidas, verificou-se que investidores que utilizam estratégias de HFT possuem uma participação de aproximadamente 70% no mercado de contratos futuros de dólar comercial. Além disso, o nível de participação é influenciado pela volatilidade de mercado e da taxa de câmbio futura, bem como o número de contratos em aberto, resultando em lucros diários de aproximadamente R$ 18 mil. Finalmente, verifica-se a existência de elevados níveis de correlação entre as estratégias utilizadas por negociadores algorítmicos e comportamento de manada, bem como a utilização de mecanismos de retroalimentação positiva. / This work presents a study about important characteristics of the adoption of high-frequency trading (HFT) strategies by investors that perform operations with USDBRL futures contracts on the Brazilian Foreign Exchange markets, such as the market share and the profits of the participants that resort to such strategies, as well as its main determinants, and the existence of patterns on the strategies adopted by high-frequency traders. It has been determined that investors that use HFT strategies possess 70% of market share on US dollar futures contracts and that its participation is influenced by markets and futures exchange rates volatility level, as well as its open interest, making an average profit of roughly 18 thousand Brazilian reals per day. Finally, it has been possible to determine the existence of high levels of correlation between the strategies adopted by high-frequency traders, as well as herding and the usage of positive feedback strategies.

Operações de alta frequência ganharam destaque nos últimos anos, tanto no mercado nacional quanto internacional, e têm atraído a atenção de reguladores, pesquisadores e da mídia. Assim, surgiu a necessidade de estudar o mercado de capitais brasileiro no contexto dos dados em alta frequência. Este estudo preocupa-se em analisar os efeitos dos avanços tecnológicos e novas formas de negociação na qualidade do mercado. Tais pontos são caracterizados pelo HFT. Gomber e Haferkorn (2013) explicam que HFT é um subgrupo das negociações com algoritmos. Os investidores HFTs são caracterizados por negociarem com seu próprio capital, manterem posições por espaços curtos de tempo, pelo alto volume de negociação e por atualizarem as ordens com frequência. A revisão da literatura permitiu delinear o termo e identificar as estratégias adotadas, os impactos positivos e negativos na qualidade de mercado, os riscos advindos da prática e medidas adotadas ou propostas para mitigar esses riscos. A contribuição decorrente das negociações em alta frequência foi analisada empiricamente com ênfase na questão da eficiência informacional do mercado nacional. Para isso, foram utilizados dados intradiários do índice Bovespa, com frequências de observação a partir de 1 minuto. Aplicações do teste de sequência para aleatoriedade e teste de razão de variância de Lo e Mackinlay (1988) evidenciaram um aumento na eficiência do mercado ao longo do período analisado, entre 2007 e 2015, para a frequência de observações de 1 minuto. Foi encontrada relação entre esse ganho em eficiência e o aumento da participação do HFT no mercado. Também foi constatado que o mercado se mostra menos eficiente quando a frequência de observação aumenta e que os ganhos em eficiência são mais acentuados para frequências maiores. Os últimos resultados fortalecem a percepção de que a melhora na eficiência está relacionada diretamente à atuação dos HFTs no mercado, haja vista a característica destes de explorarem ineficiências de preço em frações de segundos. Descreveu-se assim o mercado de capitais nessa era de alta frequência e os impactos do HFT na eficiência de mercado. Tais pontos podem ser colocados como contribuições práticas deste estudo. / High-frequency trading has gained notoriety in recent years and attracted incresing attention among policymakers, researchers and media. This brought about the need for research of high frequency data on brazilian capital market. This study aims to investigate the effects of technological advancements and new forms of trading, specially HFT, on market quality. Gomber and Haferkorn (2013, p. 97) define HFT as a subset of algorithmic trading \"characterized by short holding periods of trading positions, high trading volume, frequent order updates and proprietary trading\". The literature review made it possible to define the term and identify strategies, positive and negative impacts on market quality, risks and ways to mitigate these risks. The contribution arising from HFT was analyzed empirically with an emphasis on price efficiency in the domestic market, using intraday Bovespa index data in different frequencies. Run tests and Lo and Mackinlay (1988) variance ratio tests showed increasing efficiency over the period, between 2007 and 2015, for observations in 1 minute frequency. Relationship between this gain in price efficieny and the growth of HFT market share was found. It was found that the market is less eficiente when higher frequencies are analyzed, and that the efficiency gains are more pronounced for higher frequencies. The last results strengthen the perception that the efficiency gains are directly related to high-frequency trading, given its characteristc of exploring price inefficiencies that last fractions of seconds. The capital market in this high frequency era and the impacts of HFT on market efficiency were described in this study

Financial markets perform two major functions. The first is the provision of liquidity in order to facilitate direct investment, hedging and diversification; the second is to ensure the efficient price discovery required in order to direct resources to where they can be best utilised within an economy. How well financial markets perform these functions is critical to the financial welfare of every individual in modern economies. As an example, retirement savings across the world are mostly invested in capital markets. Hence, the functioning of financial markets is linked to the standard of living of individuals. Technological advancements and new market regulations have in recent times significantly impacted how financial markets function, with no period in history having witnessed a more rapid pace of change than the last decade. Financial markets have become very complex, with most of the order execution now done by computer algorithms. New high-tech trading venues, such as dark pools, also now play outsized roles in financial markets. A lot of the impacts of these developments are poorly understood. In the EU particularly, the introduction of the Markets in Financial Instruments Directive (MiFID) and advancements in technology have combined to unleash a dramatic transformation of European capital markets. In order to better understand the role of high-tech trading venues in the modern financial markets' trading environment generally and in the UK in particular, I conduct three studies investigating questions linked to the three major developments in financial markets over the past decade; these are algorithmic/high-frequency trading, market fragmentation and dark trading. In the first study, I examine the changing relationship between the price impact of block trades and informed trading, by considering this phenomenon within a high-frequency trading environment on intraday and inter-day bases. I find that the price impact of block trades is stronger during the first hour of trading; this is consistent with the hypothesis that information accumulates overnight during non-trading hours. Furthermore, private information is gradually incorporated into prices despite heightened trading frequency. Evidence suggests that informed traders exploit superior information across trading days, and stocks with lower transparency exhibit stronger information diffusion effects when traded in blocks, thus informed block trading facilitates price discovery. The second study exploits the regulatory differences between the US and the EU to examine the impact of market fragmentation on dimensions of market quality. Unlike the US's Regulation National Market System, the EU's MiFID does not impose a formal exchange trading linkage or guarantee a best execution price. This has raised concerns about consolidated market quality in increasingly fragmented European markets. The second study therefore investigates the impact of visible trading fragmentation on the quality of the London equity market and find a quadratic relationship between fragmentation and adverse selection costs. At low levels of fragmentation, order flow competition reduces adverse selection costs, improves market transparency and enhances market efficiency by reducing arbitrage opportunities. However, high levels of fragmentation increase adverse selection costs. The final study compares the impact of lit and dark venues' liquidity on market liquidity. I find that compared with lit venues, dark venues proportionally contribute more liquidity to the aggregate market. This is because dark pools facilitate trades that otherwise might not easily have occurred in lit venues when the spread widens and the limit order queue builds up. I also find that informed and algorithmic trading hinder liquidity creation in lit and dark venues, while evidence also suggests that stocks exhibiting low levels of informed trading across the aggregate market drive dark venues' liquidity contribution.

Cette thèse est composée de trois chapitres distincts.Dans le premier chapitre, je montre que les mesures de liquidités traditionnelles, telles que la profondeur du marché, ne sont pas toujours pertinentes pour mesurer le bien-être des investisseurs. Je construis un modèle de marché conduit par les ordres et montre qu'une offre de liquidité élevée peut correspondre à de mauvaises conditions d'éxécution pour les fournisseurs de liquidité et à un bien-être relativement faible.Dans le deuxième chapitre, je modélise la vitesse des ajustements de prix à l'arrivée de nouvelles dans les marchés conduits pas les ordres, lorsque les investisseurs ont une capacité d'attention limitée.En raison de leur attention limitée, les investisseurs suivent imparfaitement l'arrivée de nouvelles. Ainsi, les prix s'ajustent aux nouvelles après un certain délai. Ce délai diminue lorsque le niveau d'attention des investisseurs augmente.Le délai d'ajustement des prix diminue également lorsque la fréquence à laquelle les nouvelles arrivent, augmente. Le troisième chapitre présente un travail écrit en collaboration avec Thierry Foucault. Nous construisons un modèle pour expliquer en quoi le trading à haute fréquence peut générer des "mini flash crashes" (un brusque changement de prix suivi d'un retour très rapide au niveau antérieur). Notre théorie est basée sur l'idée qu'il existe une tension entre la vitesse à laquelle l'information peut être acquise et la précision de cette information. Lorsque les traders à haute fréquence mettent en oeuvre des stratégies impliquant des réactions rapides à des événements de marché, ils augmentent leur risque à réagir à du bruit et génèrent ainsi des "mini flash crashes". Néanmoins, ils augmentent l'efficience informationnelle du marché. / This dissertation is made of three distinct chapters. In the first chapter, I show that traditional liquidity measures, such as market depth, are not always relevant to measure investors' welfare. I build a limit order market model and show that a high level of liquidity supply can correspond to poor execution conditions for liquidity providers and to a relatively low welfare.In the second chapter, I model the speed of price adjustments to news arrival in limit order markets when investors have limited attention.Because of limited attention, investors imperfectly monitor news arrival. Consequently prices reflect news with delay. This delay shrinks when investors' attention capacity increases. The price adjustment delay also decreases when the frequency of new arrival increases. The third chapter presents a joint work with Thierry Foucault. We build a model to explain why high frequency trading can generate mini-flash crashes (a sudden sharp change in the price of a stock followed by a very quick rversal). Our theory is based on the idea that there is a trade-off between speed and precision in the acquisition of information. When high frequency traders implement strategies involving fast reaction to market events, they increase their risk to trade on noise and thus generate mini flash crashes. Nonetheless they increase market efficiency.

Submitted by Uirá Caiado de Castro (ucaiado@yahoo.com.br) on 2017-08-28T20:17:54Z No. of bitstreams: 1 uira_caiado_tradingRL.pdf: 1000833 bytes, checksum: d530c31d30ddfd98e5978aaaf3170959 (MD5) / Approved for entry into archive by Joana Martorini (joana.martorini@fgv.br) on 2017-08-28T21:06:42Z (GMT) No. of bitstreams: 1 uira_caiado_tradingRL.pdf: 1000833 bytes, checksum: d530c31d30ddfd98e5978aaaf3170959 (MD5) / Made available in DSpace on 2017-08-29T12:42:53Z (GMT). No. of bitstreams: 1 uira_caiado_tradingRL.pdf: 1000833 bytes, checksum: d530c31d30ddfd98e5978aaaf3170959 (MD5) Previous issue date: 2017-08-24 / O presente estudo propõe o uso de um modelo de aprendizagem por reforço para derivar uma estratégia de trading em taxa de juros diretamente de dados históricos de alta frequência do livro de ofertas. Nenhuma suposição sobre a dinâmica do mercado é feita, porém é necessário criar um simulador com o qual o agente de aprendizagem possa interagir para adquirir experiência. Diferentes variáveis relacionadas a microestrutura do mercado são testadas para compor o estado do ambiente. Funções baseadas em P&L e/ou na coerência do posicionamento das ofertas do agente são testadas para avaliar as ações tomadas. Os resultados deste trabalho sugerem algum sucesso na utilização das técnicas propostas quando aplicadas à atividade de trading. Porém, conclui-se que a obtenção de estratégias consistentemente lucrativas dependem muito das restrições colocadas na aprendizagem. / The present study proposes the use of a reinforcement learning model to develop an interest rate trading strategy directly from historical high-frequency order book data. No assumption about market dynamics is made, but it requires creating a simulator wherewith the learning agent can interact to gain experience. Different variables related to the microstructure of the market are tested to compose the state of the environment. Functions based on P&L and/or consistency in the order placement by the agent are tested to evaluate the actions taken. The results suggest some success in bringing the proposed techniques to trading. However, it is presumed that the achievement of consistently profitable strategies is highly dependent on the constraints placed on the learning task.