Occurrence of long and short term asymmetry in stock market volatilities

We introduce the notions of short and long term asymmetric effects in volatilities. With short term asymmetry we mean the conventional one, i.e. the asymmetric response of current volatility to the most recent return shocks. However, there may be asymmetries in the way the effect of past return shocks propagate over time as well. We refer to this as long term asymmetry. We propose a model that enables the study of such a feature. In an empirical application using stock market index data we found evidence of the joint presence of short and long term asymmetric effects.