This paper is dedicated to study the impact of stock spams through the analysis of the variations of volatility. We use the methodology of event studies on a sample of hundred ten firms. The results show positive and significant changes in volatility during 12 days of the event window; a...

This paper is dedicated to study the impact of the stock spams through the analysis of the variations of volumes. We use the methodology of the event studies on a sample of hundred ten firms of penny stock (firms with small size in the American market). Data cover the period of May 2002 to...

This survey appears in extension of a previous exploratory survey (Bouraoui, 2008) dedicated to the impact of stock spams on volumes. The interest of the present research is to study the impact on stock prices while taking into account the evolution of volatility over time through a GARCH (1,1)...