The thesis analyses high frequency trading, specifically its main characteristics, which make it different from algorithmic trading. Furthermore, the thesis looks closer into major risks, which are new to market, and their impact on market quality and other investors. The next chapter is dedicated to trading strategies, which are typical for high frequency trading. In conclusion, there is discussed the impact on the market quality caused by high frequency trading, namely in terms of liquidity, volatility and price discovery.

We consider Sequential Monte Carlo Approximate Bayesian Computation (SMC ABC) as a method of calibration for the use of agent based models in market micro-structure. To date, there are no successful calibrations of agent based models to high frequency trading data. Here we test whether a more sophisticated calibration technique, SMC ABC, will achieve this feat on one of the leading agent based models in high frequency trading literature (the Preis-Golke-Paul-Schneider Agent Based Model (Preis et al., 2006)). We find that, although SMC ABC's naive approach of updating distributions can successfully calibrate simple toy models, such as autoregressive moving average models, it fails to calibrate this agent based model for high frequency trading. This may be for two key reasons, either the parameters of the model are not uniquely identifiable given the model output or the SMC ABC rejection mechanism results in information loss rendering parameters unidentifiable given insucient summary statistics.

The master's thesis' objective is to study basics of high-frequency trading, especially trading at foreign exchange market. Project deals with foreign exchange data preprocessing, fundamentals of market data collecting, data storing and cleaning are discussed. Doing decisions based on poor quality data can lead into fatal consequences in money business therefore data cleaning is necessary. The thesis describes adaptive data cleaning algorithm which is able to adapt current market conditions. According to design a modular plug-in application for data collecting, storing and following cleaning has been implemented.

Högfrekvenshandel har de senaste åren växt till att bli en betydande kraft på de finansiella marknaderna och således även fått mycket medial uppmärksamhet. Den här medieuppmärksamheten intensifierades den 6: e maj 2010 då "Flash-krashen" inträffade på Dow Jones indexet i New York och påverkade marknader över hela världen. Vår avsikt med den här kandidatuppsatsen är att kritiskt granska högfrekvenshandeln som fenomen samt den diskussion som förs angående ytterligare reglering av handeln. Detta görs genom en inledande period av litteraturstudier som kompletteras med djupintervjuer av olika aktörer på marknaden. Våra resultat visar att högfrekvenshandeln inte för med sig så stora negativa effekter som media målar upp, och att den forskning som gjorts på ämnet indikerar att handeln främst tillför positiva effekter i form av ökad likviditet och minskad volatilitet. Uppsatsen behandlar även dagens regleringssituation och analyserar de förslag på åtgärder som har lagts fram på EU-nivå. Vår analys visar att många av de förslag som diskuteras är direkt missriktade och inte adresserar det egentliga problemet – en situation som kantas av oklara roller gällande tillsyn och övervakning. / High frequency trading has during the last couple of years grown to become a significant force in the financial markets, and therefore it has also gotten a lot of media attention. This media attention intensified on the 6 th of May 2010 when the so called "Flash Crash" occurred at the Dow Jones index in New York and affected markets all over the world. Our intention with this bachelor thesis is to critically examine high frequency trading as a phenomenon and the discussion that is taking place concerning further regulation of the trading. This will be done through an initial period of literature studies that will be complemented with in-depth interviews with different players in the market. Our results show that high frequency trading doesn´t come with such great negative effects as media would like to imply. The research that has been done on the subject indicates that the trading mainly adds positive effects in the form of increased liquidity and decreased volatility. The thesis will also address todays regulatory situation and analyse the proposals for additional regulation that has been discussed on an EU-level. Our analysis shows that many of the discussed proposals are directly misguided and doesn´t address the real problem – a situation that is struggling with unclear roles concerning supervision and monitoring.

High frequency trading, a version of algorithmic trading, has in recent years increased, and now represents a significant part of the trading. It has occasionally upset the public, due to its connections to events that brought negative publicity in media. Because of the complicated structure that high frequency trading have, it makes it difficult for the common man to fully understand its nature. My purpose of this work is to give a clearer picture of the various less desirable market strategies that is currently being used, and what the situation is regarding regulations. The focus is thus not on high frequency trading as a whole, nor, consequently, on the potential benefits it can bring. The approach has been to use qualitative information in the form of interviews combined with literature studies to generate a clearer picture of the current situation. The conclusion is that the development of technology has led to a situation which is not optimal regarding high frequency trading. Market confidence has been affected and its competitive neutrality has been questioned. Regulations are unfortunately lagging, relative to the market situation. Despite this, my assessment, drawn from the interviews, is that it will get better. / Högfrekvenshandel, som är en variant av algoritmhandel, har under de senaste åren ökat, och står numera för en betydande del av dagens handel. Med tiden har högfrekvenshandeln stundtals upprört allmänheten, i samband med händelser som givit negativt publicitet i media. På grund av högfrekvenshandelns komplicerade uppbyggnad har det dock varit svårt för mindre insatta att utläsa dess egentliga egenskaper. Mitt syfte med arbetet är att förmedla en tydligare bild av de olika mindre önskvärda marknadsstrategier som idag används, och hur situationen ser ut med regleringar. Fokus läggs således ej på högfrekvenshandel i sin helhet, det vill säga inte de potentiella fördelar den kan medföra. Tillvägagångssättet har varit att med kvalitativ information i form av intervjuer tillsammans med litteraturstudier skapa en tydligare bild av nuvarande situation. Slutsatsen som dras är att den tekniska utvecklingen som lett fram till dagens situation inte är optimal avseende högfrekvenshandeln. Marknadens förtroende har påverkats och dess konkurrensneutralitet ifrågasatts. Regleringarna är i förhållande till marknadssituation dessvärre eftersläpande. Trots detta är min bedömning utifrån gjorda intervjuer att det kommer att bli bättre.

The presence of toxic order ow and predatory HFT strategies in a multi-market setting are scarcely researched in the academic world. This thesis studies the toxicity levels of a set of markets by examining unconsolidated quote data and firm specific trade data. A method for deducing the markets toxicity levels is presented along with proxies for toxic order ow, namely: changes in spread and quoted volume, following a trade in a given market. We find both signs of toxicity and different toxicity levels between the markets. However, the results are lacking in statistical significance but they show that this field is of great interest for further research. Also, the methods proposed for deducing the toxicity levels are rudimentary but could serve well as a premise for further development. / Närvaron av toxic order flow och predatoriska HFT-strategier i en flermarknadsmiljö är föga studerat i den akademiska världen. Denna avhandling studerar detta på en uppsättning marknader genom att undersöka okonsoliderad quote data och firma specifika trades, och på så vis ta fram marknadernas toxicity-nivåer. En metod för att fastställa marknadernas toxicity-nivåer presenteras tillsammans med proxys för toxic order flow, mer specifikt: förändringar i spread och quotad volym, efter en handel på en given marknad. Vi finner både tecken på toxicity och olika toxicityniv åer mellan marknaderna. Resultaten saknar dock statistisk signifikans men de visar ändå på att detta område är av stort intresse för ytterligare forskning. De metoder som föreslås för att fastställa toxicity-nivåerna är rudimentära, men kan tjäna som en utgångspunkt för vidare utveckling.

Accurate forecasting of stock price movements is crucial for optimizing trade execution and mitigating risk in automated trading environments, especially when leveraging Limit Order Book (LOB) data. However, developing predictive models from LOB data presents substantial challenges due to its inherent complexities and high-frequency nature. In this thesis, the application of the General Compound Hawkes Process (GCHP) is explored to predict price volatility. Within this framework, a Hawkes process is employed to estimate the times of price changes, and a Markovian model is utilized to determine their amplitudes. The price volatility is obtained through both numerical and analytical methodologies. The performance of the GCHP is assessed on a publicly available dataset, including five distinct stocks. To enhance accuracy, the number of states in the Markov chain is gradually increased, and the advantages of incorporating a higher-order Markov chain for refined volatility estimation are demonstrated.

高頻率交易在近年已漸成為全球趨勢，在世界各主要交易所的交易型態中都占有相當的比例。高頻率交易雖因係非僅有單一策略型態的套利行為，而目前尚未有明確之定義，然簡言之，其係指於毫秒等級的微小時間內，利用複雜的計算機運算系統挾帶速度優勢來進行迅速探測出市場上股票或期貨微小的價格差異並從中套利之交易模式。高頻率交易的特性是「交易頻繁，但每次獲利微薄」，且通常是當沖交易。然而，此種立基於快速撮合的逐筆交易制度以及資訊軟硬體設備進步而生之新型交易模式，除能帶來增加交易市場流動性、促進市場活絡等優點以外，亦藏有使股市因無意向成交而產生劇烈波動或造成市場秩序不公平等風險，如著名的美國2010年閃電崩盤即為一例。 我國證券市場的交易制度幾經更迭，現行所採之集合競價的撮合間隔時間一路從20秒降至現行的5秒，然仍遲未採行各國趨勢之逐筆交易制度。現任證交所董事長施俊吉對此也於2016年12月13日受訪時指出，集合競價交易方式已屬老式且落伍，逐筆交易已水到渠成，運作尚有賴券商業者大力配合。只要券商準備好即可隨時啟動。 證券交易市場首重公平性，此於我國證券交易法立法目的即可觀之。我國雖因未採行逐筆交易制度，目前尚未面臨高頻率交易之挑戰，然於可預見之未來，我國實施逐筆交易制度後，高頻率交易的產生以及比重無可避免地將有隨之增加之可能。此時我國證券交易市場所將面臨的，即高頻率交易究竟有無促進市場效率、抑或破壞市場公平性；以及我們又該如何將之規範以兼顧市場整體利益與投資人保護等考驗。 本論文以現行我國交易制度的發展動向為脈絡，並以未雨綢繆之角度初探高頻率交易此一議題，藉參考他國就此交易模式之制度與規範方向，自我國現行證券交易法之制度下進行檢視及討論，藉此試提出於我國推行逐筆交易後，發生高頻率交易時之相關配套建議以及對投資人的保護措施，做為我國日後實際推行逐筆交易制度與高頻率交易時之參考依據。 / High-frequency trading (HFT) has become a global trend in recent years. It accounts for a considerable proportion in the world's major exchanges. HFT is not only a single strategy for the type of arbitrage behavior; hence, there is still no clear definition of it. But in short, it refers to a type of algorithmic trading characterized by "frequent transactions with minute profit". Despite the benefit of increasing the liquidity of market and promoting market activity, it also has some disadvantages such as interfering the market order and the risk of unfairness. The well-known case, Flash Crash, of America in 2010 is so one example of HFT. The securities market trading system of Taiwan, Call Auction, has changed several times. The interval of the auction collecting and matching time has been all the way from 20 seconds down to the 5 seconds in current. But the final goal, Trade by Trade Matching transaction, has not yet been adopted so far. In December of 2016, the current chairman of Taiwan Stock Exchange said that Call Auction transaction is now old-fashioned and outdated, Trade by Trade Matching transaction has become a matter of course. Trade by Trade Matching transaction is just right around the corner, and it’s ready to launch as long as the brokers are ready. Fairness is the first priority in securities market. While Taiwan has not yet adopted the Trade by Trade Matching transaction and has not yet faced the challenges of HFT, Taiwan will no doubt implement it in the foreseeable future, and therefore the possibility of the appearance and the proportion of HFT in our market will be increasing. At the same time, HFT will be faced with whether it will promote market efficiency or undermine the fairness of the market. How should we regulate it and how to protect the interests of investors and the overall benefit of our market will also become our tests. This thesis takes the development trend of current trading system in Taiwan as a starting point and probes into the issue of HFT from the view of precaution. By referring to the trading system and regulations toward HFT of other countries, this thesis try to propose relevant suggestions and protection measures for investors and appropriate regulations of market after the implementation of Trade by Trade Matching transaction and the embracement of HFT in Taiwan.

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

Purpose: 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. 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. Background: 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. Method: The research has been carried out as an exploratory, descriptive and analytical qualitative study. We have conducted case studies of 7 companies that are implementing, or evaluating the implementation, of ATS. The data was collected through interviews. Conclusion: 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 required level of competence-sharing and complexity of implementation.