Modelización de series temporales complejas: de las redes de telecomunicación a los mercados financieros

Este trabajo aborda el problema de modelizar sistemas din´amicos reales a partir del estudio de sus series temporales, usando una formulaci´on est´andar que pretende ser una abstracci´on universal de los sistemas din´amicos, independientemente de su naturaleza determinista, estoc´astica o h´ıbrida. Se parte de modelizaciones separadas de sistemas deterministas por un lado y estoc´asticos por otro, para converger finalmente en un modelo h´ıbrido que permite estudiar sistemas gen´ericos mixtos, esto es, que presentan una combinaci´on de comportamiento determinista y aleatorio. Este modelo consta de dos componentes, uno determinista consistente en una ecuaci´on en diferencias, obtenida a partir de un estudio de autocorrelaci´on, y otro estoc´astico que modeliza el error cometido por el primero. El componente estoc´astico es un generador universal de distribuciones de probabilidad, basado en un proceso compuesto de variables aleatorias, uniformemente distribuidas en un intervalo variable en el tiempo. Este generador universal es deducido en la tesis a partir de una nueva teor´ıa sobre la oferta y la demanda de un recurso gen´erico. El modelo resultante puede formularse conceptualmente como una entidad con tres elementos fundamentales: un motor generador de din´amica determinista, una fuente interna de ruido generadora de incertidumbre y una exposici´on al entorno que representa las interacciones del sistema real con el mundo exterior. En las aplicaciones estos tres elementos se ajustan en base al hist´orico de las series temporales del sistema din´amico. Una vez ajustados sus componentes, el modelo se comporta de una forma adaptativa tomando como inputs los nuevos valores de las series temporales del sistema y calculando predicciones sobre su comportamiento futuro. Cada predicci´on se presenta como un intervalo dentro del cual cualquier valor es equipro- bable, teniendo probabilidad nula cualquier valor externo al intervalo. De esta forma el modelo computa el comportamiento futuro y su nivel de incertidumbre en base al estado actual del sistema. Se ha aplicado el modelo en esta tesis a sistemas muy diferentes mostrando ser muy flexible para afrontar el estudio de campos de naturaleza dispar. El intercambio de tr´afico telef´onico entre operadores de telefon´ıa, la evoluci´on de mercados financieros y el flujo de informaci´on entre servidores de Internet son estudiados en profundidad en la tesis. Todos estos sistemas son modelizados de forma exitosa con un mismo lenguaje, a pesar de tratarse de sistemas f´ısicos totalmente distintos. El estudio de las redes de telefon´ıa muestra que los patrones de tr´afico telef´onico presentan una fuerte pseudo-periodicidad semanal contaminada con una gran cantidad de ruido, sobre todo en el caso de llamadas internacionales. El estudio de los mercados financieros muestra por su parte que la naturaleza fundamental de ´estos es aleatoria con un rango de comportamiento relativamente acotado. Una parte de la tesis se dedica a explicar algunas de las manifestaciones emp´ıricas m´as importantes en los mercados financieros como son los “fat tails”, “power laws” y “volatility clustering”. Por ´ultimo se demuestra que la comunicaci´on entre servidores de Internet tiene, al igual que los mercados financieros, una componente subyacente totalmente estoc´astica pero de comportamiento bastante “d´ocil”, siendo esta docilidad m´as acusada a medida que aumenta la distancia entre servidores. Dos aspectos son destacables en el modelo, su adaptabilidad y su universalidad. El primero es debido a que, una vez ajustados los par´ametros generales, el modelo se “alimenta” de los valores observables del sistema y es capaz de calcular con ellos comportamientos futuros. A pesar de tener unos par´ametros fijos, la variabilidad en los observables que sirven de input al modelo llevan a una gran riqueza de ouputs posibles. El segundo aspecto se debe a la formulaci´on gen´erica del modelo h´ıbrido y a que sus par´ametros se ajustan en base a manifestaciones externas del sistema en estudio, y no en base a sus caracter´ısticas f´ısicas. Estos factores hacen que el modelo pueda utilizarse en gran variedad de campos. Por ´ultimo, la tesis propone en su parte final otros campos donde se han obtenido ´exitos preliminares muy prometedores como son la modelizaci´on del riesgo financiero, los algoritmos de routing en redes de telecomunicaci´on y el cambio clim´atico. Abstract This work faces the problem of modeling dynamical systems based on the study of its time series, by using a standard language that aims to be an universal abstraction of dynamical systems, irrespective of their deterministic, stochastic or hybrid nature. Deterministic and stochastic models are developed separately to be merged subsequently into a hybrid model, which allows the study of generic systems, that is to say, those having both deterministic and random behavior. This model is a combination of two different components. One of them is deterministic and consisting in an equation in differences derived from an auto-correlation study and the other is stochastic and models the errors made by the deterministic one. The stochastic component is an universal generator of probability distributions based on a process consisting in random variables distributed uniformly within an interval varying in time. This universal generator is derived in the thesis from a new theory of offer and demand for a generic resource. The resulting model can be visualized as an entity with three fundamental elements: an engine generating deterministic dynamics, an internal source of noise generating uncertainty and an exposure to the environment which depicts the interactions between the real system and the external world. In the applications these three elements are adjusted to the history of the time series from the dynamical system. Once its components have been adjusted, the model behaves in an adaptive way by using the new time series values from the system as inputs and calculating predictions about its future behavior. Every prediction is provided as an interval, where any inner value is equally probable while all outer ones have null probability. So, the model computes the future behavior and its level of uncertainty based on the current state of the system. The model is applied to quite different systems in this thesis, showing to be very flexible when facing the study of fields with diverse nature. The exchange of traffic between telephony operators, the evolution of financial markets and the flow of information between servers on the Internet are deeply studied in this thesis. All these systems are successfully modeled by using the same “language”, in spite the fact that they are systems physically radically different. The study of telephony networks shows that the traffic patterns are strongly weekly pseudo-periodic but mixed with a great amount of noise, specially in the case of international calls. It is proved that the underlying nature of financial markets is random with a moderate range of variability. A part of this thesis is devoted to explain some of the most important empirical observations in financial markets, such as “fat tails”, “power laws” and “volatility clustering”. Finally it is proved that the communication between two servers on the Internet has, as in the case of financial markets, an underlaying random dynamics but with a narrow range of variability, being this lack of variability more marked as the distance between servers is increased. Two aspects of the model stand out as being the most important: its adaptability and its universality. The first one is due to the fact that once the general parameters have been adjusted , the model is “fed” on the observable manifestations of the system in order to calculate its future behavior. Despite the fact that the model has fixed parameters the variability in the observable manifestations of the system, which are used as inputs of the model, lead to a great variability in the possible outputs. The second aspect is due to the general “language” used in the formulation of the hybrid model and to the fact that its parameters are adjusted based on external manifestations of the system under study instead of its physical characteristics. These factors made the model suitable to be used in great variety of fields. Lastly, this thesis proposes other fields in which preliminary and promising results have been obtained, such as the modeling of financial risk, the development of routing algorithms for telecommunication networks and the assessment of climate change.

UMA ANÁLISE DA RELAÇÃO ENTRE VARIÁVEIS MACROECONÔMICAS E O COMPORTAMENTO DAS AÇÕES DE MAIOR LIQUIDEZ DO ÍNDICE IBOVESPA

As ações de maior liquidez do índice IBOVESPA, refletem o comportamento das ações de um modo geral, bem como a relação das variáveis macroeconômicas em seu comportamento e estão entre as mais negociadas no mercado de capitais brasileiro. Desta forma, pode-se entender que há reflexos de fatores que impactam as empresas de maior liquidez que definem o comportamento das variáveis macroeconômicas e que o inverso também é uma verdade, oscilações nos fatores macroeconômicos também afetam as ações de maior liquidez, como IPCA, PIB, SELIC e Taxa de Câmbio. O estudo propõe uma análise da relação existente entre variáveis macroeconômicas e o comportamento das ações de maior liquidez do índice IBOVESPA, corroborando com estudos que buscam entender a influência de fatores macroeconômicos sobre o preço de ações e contribuindo empiricamente com a formação de portfólios de investimento. O trabalho abrangeu o período de 2008 a 2014. Os resultados concluíram que a formação de carteiras, visando a proteção do capital investido, deve conter ativos com correlação negativa em relação às variáveis estudadas, o que torna possível a composição de uma carteira com risco reduzido.

Testing co-volatility spillovers for natural gas spot, futures and ETF spot using dynamic conditional covariances

There is substantial empirical evidence that energy and financial markets are closely connected. As one of the most widely-used energy resources worldwide, natural gas has a large daily trading volume. In order to hedge the risk of natural gas spot markets, a large number of hedging strategies can be used, especially with the rapid development of natural gas derivatives markets. These hedging instruments include natural gas futures and options, as well as Exchange Traded Fund (ETF) prices that are related to natural gas stock prices. The volatility spillover effect is the delayed effect of a returns shock in one physical, biological or financial asset on the subsequent volatility or co-volatility of another physical, biological or financial asset. Investigating volatility spillovers within and across energy and financial markets is a crucial aspect of constructing optimal dynamic hedging strategies. The paper tests and calculates spillover effects among natural gas spot, futures and ETF markets using the multivariate conditional volatility diagonal BEKK model. The data used include natural gas spot and futures returns data from two major international natural gas derivatives markets, namely NYMEX (USA) and ICE (UK), as well as ETF data of natural gas companies from the stock markets in the USA and UK. The empirical results show that there are significant spillover effects in natural gas spot, futures and ETF markets for both USA and UK. Such a result suggests that both natural gas futures and ETF products within and beyond the country might be considered when constructing optimal dynamic hedging strategies for natural gas spot prices.

International Capital Flows and Monetary Policy Spillovers

This dissertation examines the drivers and implications of international capital flows. The overarching motivation is the observation that countries not at the centre of global financial markets are subject to considerable spillovers from centre countries, notably from their monetary policy. I present new empirical evidence on the determinants of the observed patterns of international capital flows and monetary policy spillovers, and study their effect on both financial markets and the real economy. In Chapter 2 I provide evidence on the determinants of a puzzling negative correlation observed between productivity growth and net capital inflows to developing and emerging market economies (EMEs) since 1980. By disaggregating net capital inflows into their gross components, I show that this negative correlation is explained by capital outflows related to purchases of very liquid assets from the fastest growing countries. My results suggest a desire for international portfolio diversification in liquid assets by fast growing countries is driving much of the original puzzle. In the reminder of my dissertation I pivot to study the foreign characteristics that drive international capital flows and monetary policy spillovers, with a particular focus on the role of unconventional monetary policy in the United States (U.S.). In Chapter 3 I show that a significant portion of the heterogeneity in EMEs' asset price adjustment following the quantitative easing operations by the Federal Reserve (the Fed) during 2008-2014 can be explained by the degree of bilateral capital market frictions between these countries and the U.S. This is true even after accounting for capital controls, exchange rate regimes, and domestic monetary policies. Chapter 4, co-authored with Michal Ksawery Popiel, studies unconventional monetary policy in a small open economy, looking specifically at the case of Canada since the global financial crisis. We quantify the effect Canadian unconventional monetary policy shocks had on the real economy, while carefully controlling for and quantifying spillovers from U.S. unconventional monetary policy. Our results indicate that the Bank of Canada's unconventional monetary policy increased Canadian output significantly from 2009-2010, but that spillovers from the Fed's policy were even more important for increasing Canadian output after 2008.

The meaning of Cyprus; moving toward banking union. CEPS Commentary, 8 April 2013

While acknowledging that Cyprus is too small to matter for global financial markets, this Commentary finds that its case could turn out to become a very important precedent for the way European policy-makers deal with future banking problems and the plans for a ‘banking union’.

A Viable Alternative to Basel III Prudential Capital Rules. CEPS Policy Brief No. 291, May 2013

Stefano Micossi argues in this paper that the Basel framework for bank prudential requirements is deeply flawed and that the Basel III revision has failed to correct these flaws, making the system even more complicated, opaque and open to manipulation. In practice, he finds that the present system does not offer regulators and financial markets a reliable capital standard for banks and its divergent implementation in the main jurisdictions of the European Union and the United States has broken the market into special fiefdoms governed by national regulators in response to untoward special interests. The time is ripe to stop tinkering with minor adjustment and revisions in order to rescue the system, because the system cannot be rescued. In response to the current situation, Micossi calls for abandoning reference to risk-weighted assets calculated by banks with their internal risk management models for the determination of banks’ prudential capital, together with the preoccupation with the asset side of banks in correcting for risk exposure. He suggests that the alternative may be provided by a combination of a straight capital ratio and a properly designed deposit insurance system. It is a logical, complete and much less distortive alternative; it would serve better the cause of financial stability as well as the interest of the banks in clear, transparent and level playing field.

The response speed of the International Monetary Fund. Bruegel Working Paper 2013/03, 16 July 2013

The more severe a financial crisis, the greater has been the likelihood of its management under an IMF-supported programme and the shorter the time from crisis onset to programme initiation. Political links to the United States have increased programme likelihood but have prompted faster response mainly for ‘major’crises. Over time, the IMF’s response has not been robustly faster, but the time sensitivity to the more severe crises and those related to fixed exchange rate regimes did increase from the mid-1980s. Similarly, democracies had tended to stall programme initiation but have become more supportive of financial markets’ demands for quicker action.

Reviewing the EU's market abuse rules. ECMI Policy Brief No. 19, 27 February 2012

Updated May 2012 and reposted: In 2011, an EU legislative package on market abuse was proposed, which comprises two sets of documents: 1) a draft Regulation that will largely replace the existing Market Abuse Directive (MAD) and the level 2 measures; and a new Directive dealing with criminal sanctions. Market abuse rules are needed to ensure market integrity and investor confidence, and to allow companies to raise capital and contribute to economic growth, thereby increasing employment. This ECMI Policy Brief argues that rules on market abuse should be technically well designed, proportionate and crystal clear, but also subject to more efficient and harmonised supervision than before. The paper focuses particularly on the draft Regulation. The use of a regulation is welcome, as (in integrated financial markets) abuses should be regulated in a harmonised manner by member states, which has not always been the case, as the 2007 report from the European Securities Markets Expert (ESME) Group extensively demonstrated. At the same time, this paper criticises some of the provisions contained in the draft Regulation, notably the new notion of inside information not to abuse (Art. 6(e)) and the unchanged definition of inside information for listed companies to disclose, and it proposes new definitions. The extension of disclosure obligations to issuers whose shares are traded on demand only on ‘listing’ multilateral trading facilities is also widely criticised. Other comments deal with the proposed rules on managers’ transactions, insiders’ lists and accepted market practices.

European banking disunion. CEPS Commentary, 14 November 2013

In this CEPS Commentary Daniel Gros argues that the purpose of the euro was to create fully integrated financial markets; but, since the start of the financial crisis in 2008, markets have increasingly separated along national lines. So the future of the eurozone depends crucially on whether that trend continues or is reversed and Europe’s financial markets in the end become fully integrated. But either outcome would be preferable to something in between – neither fish nor fowl. Unfortunately, that is where the eurozone appears to be headed.

Transaction Banking: Respecting its role in the real economy. ECRI Policy Brief No. 6, 6 December 2013

This paper sketches the main features and issues related to recent market developments in global transaction banking (GTB), particularly in trade finance, cash management and correspondent banking. It describes the basic functioning of the GTB, its interaction with global financial markets and related implications of global regulatory developments such as Basel III. The interest in GTB has recently increased, since its low-risk profile, tendency to follow growth rates worldwide and relative independence from other financial instruments became an interesting diversification opportunity both for banks’ business models and for investors. Transaction banking has been a resilient business during the crisis, despite the reduction in world trade figures. In the post crisis period, GTB must cope with new challenges related to increased local and global regulation and the risk of inconsistency in regulatory approaches, which could negatively impact the global network and increased competition by new market entrants. Increased sophistication of corporate clients, as well as the pressure to develop and adopt technological innovations more quickly than other areas of banking continues to impact the business. The future of the industry closely depends on its ability to adjust to complex regulatory developments while at the same time being able to operate a global and efficient network.

The Sovereign Debt Crisis: Placing a curb on growth (updated edition). CEPS Paperbacks. September 2013

This book provides an update to the major 2012 study by the same authors on the dual role of the public sector as the provider of the ultimate riskless asset and, at the same time, the source of a potential major systemic risk. In this second edition, Brender and his colleagues concentrate again on the tension between the need for the public sector to sustain demand in the face of a deleveraging private sector and the longer-term challenges of sustainability for fiscal policy in the major developed economies of the US, Japan and the euro area. In short, their principal thesis is that sovereign debt is in crisis. This crisis is apparent in the euro area, but it is also real, if at present only latent, in the US and Japan. The book shows how this process has evolved in these three big developed economies – and how their policy choices impact on global financial markets.

Mellowing Meroni: Hows ESMA can help build the single market. CEPS Commentaries, 18 February 2014

In examining the long-awaited opinion given January 22nd by the CJEU in the case concerning the European Securities and Markets Authority (ESMA), this Commentary argues that the ruling is important for the insights it yields into the modern understanding of the Meroni non-delegation doctrine. The authors, Jacques Pelkmans and Marta Simoncini, aim to extract the potential implications of the ESMA case for the place and significance of the Meroni doctrine in building up the single market. They demonstrate that the ESMA case is yet another manifestation of a slow process of “mellowing Meroni’, which is a critical condition for a new single market strategy aiming to end the remaining fragmentation of the single market – not only in financial markets but also in network industries – and to ensure its ‘proper functioning’.

Bail-in Provisions in State Aid and Resolution Procedures: Are they consistent with systemic stability? CEPS Policy Brief No. 318, 21 May 2014

This CEPS Policy Brief examines the provisions for bail-in in the European Union – that is, the principle whereby any public measure to recapitalise a bank with insufficient prudential capital must be preceded by a write-down or conversion into equity of creditors’ claims – in state aid policies and in the new resolution framework for failing banks, with two aims: i) to assess whether and how they are coordinated and ii) more importantly, whether they address satisfactorily the question of systemic stability that may arise when investors fear that creditors’ claims are likely to be bailed-in in a bank crisis. The issue is especially relevant in the present context, as the comprehensive assessment exercise underway for EU banks falling under the direct supervision of the European Central Bank may lead supervisors to require substantial capital injections simultaneously for many of the banks involved, possibly shaking investors’ confidence across EU banking markets. The authors conclude that the two sets of rules are, broadly speaking, mutually consistent and that they already contain sufficient safeguards to address systemic stability concerns. However, the balance of the elements underpinning the European Commission’s decisions in individual cases may not be clear to bank creditors and potential investors in financial markets. The impression of unneeded rigidity on this very sensitive issue has been heightened by official statements over-emphasising that each case will be assessed individually under competition rules, thus feeding the concern that the systemic dimension of the issue may have been underestimated. Therefore, further clarification by the Commission may be needed on how the various criteria will be applied during the ongoing transition to banking union – perhaps through a new communication completing the state aid framework for banks in view of the adoption of the new resolution rules.

Flexibility clauses in the Stability and Growth Pact: No need for revision. CEPS Policy Brief No. 319, 24 July 2014

This Policy Brief offers an in-depth review of the Stability and Growth Pact (SGP) and looks at whether the margins of flexibility within existing rules are sufficient in the current climate of low growth, or whether there is a need to broaden them. The issue is especially relevant as the changing economic environment is raising fresh questions about whether the EU’s current common economic policies are able to manage dismal growth and low inflation. The fragile state of confidence in financial markets and the unresolved but inevitable questions of moral hazard linked to lax fiscal policies mean that no large-scale fiscal expansion to support the recovery of economic activity is feasible. The discussion may therefore only concern the scope within the SGP to accommodate an unexpected drop in economic activity and to provide room for the implementation of structural reforms. Here, we analyse the flexibility clauses of the Stability and Growth Pact under three headings; namely “exceptional circumstances”, “structural reforms and other relevant factors”, and the “investment clause”. Recommendation: Our main conclusion is that the SGP contains sufficient flexibility to accommodate an unexpected drop in economic activity and has the margins needed to finance structural reforms during the transition to the new regime. We therefore see no need to change the existing rules of the SGP. We believe that the ongoing debate about a fresh growth strategy for the eurozone and the European Union would greatly benefit from removing from the Council table ill-formulated and unnecessary demands for greater flexibility in the SGP.

The EU-Ukraine-Russia Sanctions Triangle. CEPS Commentary, 13 October 2014

The EU and the US have been stepping up sanctions against Russia because the Kremlin has broken every basic rule of the pan-European security order enshrined in the Helsinki Treaty of 1975. The effective closure of financial markets for Russia’s big businesses now has serious bite. The Kremlin’s counter-sanctions are marginal. Russia’s actual and threatened trade sanctions against Ukraine, alongside its aggression over Crimea and east Ukraine, mean that it has cast itself in the image of an enemy for most Ukrainians. Europe’s trust of the Kremlin has sunk to its lowest level since pre-Gorbachev times. If Russia were to switch to a sincerely cooperative, long-term peace mode with Ukraine, the EU and the US would no doubt be happy to scrap the sanctions. In the absence of this, however, the logic would be for the EU and the US to sustain the most significant economic sanctions for as long as it takes, with preparedness to intensify them.