Sofiane Aboura

The reactive volatility model

The article focuses on the leverage effect modeling as a form of stochastic processes through the volatility model. It states that leverage effect is characterized by a subsequent stock price dropping and increase in volatility. It mentions that the first model that describes the volatility and price relations known as Constant Elasticity of Variance Model (CEV) was developed by Cox.

Systematic Credit Risk: CDX Index Correlation and Extreme Dependence

Dependence is an important issue in credit risk portfolio modeling and pricing. We discuss a straightforward common factor model of credit risk dependence, which is motivated by intensity models such as Duffie and Singleton (1998), among others. In the empirical analysis, we study dependence under the risk-neutral measure using credit default swap (CDS) spread data of liquid large-cap U.S. obligors. The proxy for the commonfactor is the DJ CDX.NA.IG index. We document that (i) the CDX factor is significant but has low explanatory power, (ii) factor sensitivities show distinct time-varying nature and that (iii) systematic credit risk shows asymmetric extreme factor dependence, where extreme dependence is present for upward CDX movements only. This finding from an EVT-copula approach is what is predicted by various intensity models of joint defaults.

Disentangling Crashes from Tail Events

The study of tail events has become a central preoccupation for academics, investors and policy makers, given the recent financial turmoil. However, the question on what differentiates a crash from a tail event remains unsolved. This article elaborates a new definition of stock market crash taking a risk management perspective based on an augmented extreme value theory methodology. An empirical test on the French stock market (1968–2008) indicates that it experienced only two crashes in 2007–2008 among the 12 identified over the whole period.

Should Employers Pay Their Employees Better

Should employers pay their employees better? Although this question might appear provoking because lowering production costs remains a cornerstone of the contemporary economy, we present new evidence highlighting the benefits a company might reap by paying its employees better. We introduce an original methodology that uses firm economic and financial indicators to build factors that are more uncorrelated than in the classical Fama and French setting. As a result, we uncover a new anomaly in asset pricing that is linked to the average employee remuneration: the more a company spends on salaries and benefits per employee, the better its stock performs, on average. We ensure that the abnormal performance associated with employee remuneration is not explained by other factors, such as stock indexes, capitalization, book-to-market value, or momentum. A plausible rational explanation of the remuneration anomaly involves the positive correlation between pay and employee performance.

The place of gold in the cross-market dependencies

Abstract This paper investigates the inter-relationships between the gold price on the one hand, other precious metals (e.g. silver, palladium, platinum) and asset markets (e.g. stocks, bonds, crude oil) on the other hand. The econometric methodology relies on the Markov-switching BEKK model by Haas and Mittnik (2008) that captures time-varying correlations and bull-bear regimes for bivariate specifications. The model is applied to daily data from 1988 to 2013. The main results indicate that gold’s influence, through return and/or volatility spillovers, seems almost intact whatever the economic regime. Robustness checks of the statement that gold occupies a special place among commodities are provided under the form of a multi-asset portfolio management exercise.

Can Exposure to Tail Risk Explain Size, Book-to-Market, and Idiosyncratic Volatility Anomalies?

We examine the impact of aggregate tail risk on return dynamics of size, book-to-market ratio, and idiosyncratic volatility sorted portfolios. Using changes in VIX Tail Hedge Index (ΔVXTH) as a proxy for aggregate tail risk, and controlling for market, size, book-to-market, and aggregate volatility risk, we document significant portfolio return exposures to tail risk. In particular, portfolios that contain small, value and volatile stocks exhibit consistently positive and statistically significant tail risk betas, whereas portfolios of big, growth and non-volatile stocks exhibit negative tail risk betas. We posit that due to their positive tail risk exposures, tail risk-averse investors demand extra compensation to hold small, value, and high idiosyncratic volatility stocks. Our results offer a tail risk-based explanation to size, value, and idiosyncratic volatility anomalies.

A Model of Self-Regulation in Banking Industry

This article derives a model of self-regulation where banks issue insurance products to hedge their leverage ratio. This approach is an alternative policy to Basel regulation for controlling systemic risk without increasing equity level. We show some conditions under which the model can be applied to each of the 22 banks of 5 major countries from 2005 to 2012.

Is There Any Black Swan Hidden in the Oil Markets

Since the last three decades, advanced economies have been facing a substantial rise not only in the crude oil price but also in the oil price volatility. Quantifying the tail risk has become a prominent issue for investment decisions and risk management. This article reveals the existence of a tail risk hidden in the oil market by applying, for the first time, an extreme value theory analysis with a quantile regression procedure. An empirical test is carried out on the daily West Texas Intermediate (WTI) crude oil prices from 1983 to 2011. The main results indicate that the WTI becomes extreme from a daily variation of 3.50% and -2.50%. In addition, the maximum one-day variation which should be exceeded in one year every century is 20% and -30%.

Testing the fed and the Graham & Dodd models: asymmetric vs. symmetric adjustment

We examine the empirical validity of the Fed model and the Graham & Dodd model for five countries and over a time period spanning three decades by applying the Enders and Granger (1998) and Enders and Siklos (2001) threshold unit-root and cointegration tests. Our results support the hypothesis that the adjustment back to equilibrium is asymmetric.

Pricing Cac 40 Index Options Under Asymmetry of Information

This article analyses, for the first time, the financial impact on the French market of September 11th, 2001. Was there any information asymmetry around this date? How deep was the reaction of the French investors? This study measures the magnitude of the shock in the stock price process.