Performance of Empirical Risk Minimization for Linear Regression with Dependent Data

This paper establishes bounds on the performance of empirical risk minimization for large-dimensional linear regression. We generalize existing results by allowing the data to be dependent and heavy-tailed. The analysis covers both the cases of identically and heterogeneously distributed observations. Our analysis is nonparametric in the sense that the relationship between the regressand and the regressors is not specified. The main results of this paper show that the empirical risk minimizer achieves the optimal performance (up to a logarithmic factor) in a dependent data setting

EVALUATING THE ACCURACY OF TAIL RISK FORECASTS FOR SYSTEMIC RISK MEASUREMENT

In this paper we address how to evaluate tail risk forecasts for systemic risk measurement. We propose two loss functions, the Tail Tick Loss and the Tail Mean Square Error, to evaluate, respectively, CoVaR and MES forecasts. We then analyse CoVaR and MES forecasts for a panel of top US financial institutions between 2000 and 2012 constructed using a set of bivariate DCC-GARCH-type models. The empirical results highlight the importance of using an appropriate loss function for the evaluation of such forecasts. Among other findings, the analysis confirms that the DCC-GJR specification provides accurate predictions for both CoVaR and MES, in particular for the riskiest group of institutions in the panel (Broker-Dealers)

Entropy and Efficiency of the ETF Market

We investigate the relative information efficiency of financial markets by measuring the entropy of the time series of high frequency data. Our tool to measure efficiency is the Shannon entropy, applied to 2-symbol and 3-symbol discretisations of the data. Analysing 1-min and 5-min price time series of 55 Exchange Traded Funds traded at the New York Stock Exchange, we develop a methodology to isolate residual inefficiencies from other sources of regularities, such as the intraday pattern, the volatility clustering and the microstructure effects. The first two are modelled as multiplicative factors, while the microstructure is modelled as an ARMA noise process. Following an analytical and empirical combined approach, we find a strong relationship between low entropy and high relative tick size and that volatility is responsible for the largest amount of regularity, averaging 62% of the total regularity against 18% of the intraday pattern regularity and 20% of the microstructure

Choosing Motherhood : The complexities of pregnancy decision-making among young black women 'looked after' by the State

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivative Works License, which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited. Copyright 2013 the Authors, published by Elsevier Ltd.Objective: This paper addresses the experiences of a group of young black teenage mothers looked after by the State, most of whom were also either migrants or asylum seekers. The paper explores the experience of discovery of pregnancy, attempts to seek professional help and the eventual decision to continue with the pregnancy. Design: An interpretative study with in-depth interviews. Settings: Interviews were carried out in the participants’ homes and focussed on their experiences of pregnancy decision-making. Participants: 15 young women (aged 16-19), from black minority ethnic groups, with a history of care (past or present), currently pregnant or mothers of a child no older than two years of age. Findings: All the pregnancies were unexpected: eight of the informants conceived as a result of rape and seven while in a relationship. All the young women chose motherhood over abortion despite their complex social and pregnancy background. Conclusions: The importance of social positioning of migrants in terms of the cluster of negative aspects and environmental disadvantage generally experienced by most immigrants in the host country is raised in this paper. Care practices of pregnant women with complex social factors were little observant of woman-centred care approaches.Peer reviewedFinal Published versio

News as changing texts: Corpora, methodologies and analysis (second edition)

The updated and revised edition of this volume maintains its focus on the dialectic interrelation between \u2018news\u2019 and \u2018change\u2019. News is intended as a textual type in its evolutionary \u2013 and revolutionary \u2013 development, while change is discussed with reference to the form, content and structure of news texts. The news texts in question range from the first forms of periodical news in the seventeenth century up to the news blogs and social media of the present day. Divided into four chapters, representing key historical moments in the process of news writing, each chapter makes use of a set of corpora specifically designed to suit the needs of scholars working in those particular fields. Topics that the authors examine include pronominal usage and the interrelationship between news writer and reader, heads and headlines, the language of advertisements and other text classes, the trend towards conversationalization, and impartiality and \u2018perspective\u2019 in modern-day news. These and other topics, coupled with the varying corpora that are exploited to analyse them, call into question basic methodological issues that are examined from different perspectives. Throughout the volume, the authors contextualise the news publications of the day so as to better understand the continuous process of adjustment and renewal that news texts are subject to over time