Modeling Stock Returns Using Asymmetric Garch-Icapm with Mixture and Heavy-Tailed Distributions : An Application to COVID-19 Pandemic Forecasts

COVID-19 pandemic is an extreme event that created a turmoil in stock markets around the world. This unexpected circumstance poses a critical question whether the prevailing models can help predict the plummets of indices, hence the returns. In this study, we model the stock returns using univariate classical and asymmetric generalized autoregressive conditional heteroskedastic (GARCH) with the innovation following (1) mixture of generalized Pareto and Gaussian distributions and (2) generalized error distribution.We also employ the parallel griddy Gibbs (GG) sampling, which is a Markov chain Monte Carlo method, to facilitate the parameter estimation. Our simulation study shows that the GG estimation method outperforms the benchmark quasi-maximum likelihood estimation method. We then proceed to the empirical study of seven stock markets where the results from the in-sample period before the COVID-19 pandemic justify the use of the proposed GARCH models. The out-of-sample forecasts during the early COVID-19 period also show satisfactory results