Purpose: The main goal of this thesis is to investigate whether the French market is weak and semi-strong from efficient. The weak form efficiency is tested by examining the existence of January effect in the CAC 40 index for ten years. The semi-strong form is also tested by examining the reaction of the CAC 40 index. To one terrorist attack, mainly “Charlie Hebdo” terrorist attack. Design/methodology/approach: A quantitative research design has been employed using two different methodologies. The first one is an ARCH model and its extensions in order to test the January effect, and the second ...