Modeling Stock Returns Volatility in Nigeria: Applications of GARCH Family Models

Abstract

This study examines volatility and its stylized facts in Nigerian stock market using daily quotations of Guinness Plc and 7UP Plc stock prices for the period 2nd January 1995 to 31st December, 2016. The study employs basic GARCH (1,1) to examine the symmetric properties of the series while the asymmetric EGARCH (1,1) and Asymmetric Power ARCH, APACH (1,1) are employed to investigate asymmetry and leverage effects in the return series.  The results of symmetric GARCH (1,1) shows volatility clustering, high persistence of shocks and mean reverting behaviour for both returns. The results of the asymmetric EGARCH (1,1) and asymmetric power ARCH, APARCH (1,1) showed the presence of asymmetry with absence of leverage effects in Guinness Plc stock returns and the presence of asymmetry and leverage effects in 7UP Plc stock returns. This result suggests that positive shocks increase volatility more than negative shocks of the same magnitude in Guinness Plc whereas negative shocks generate more volatility than positive shocks of the same magnitude in 7UP Plc returns. The choice of heavy-tailed distributions (GED and student's t) in estimating volatility in this study confirmed the existence of fat tails in Nigerian stock returns. The study recommends some policy implications for investors and policymakers in Nigerian stock market.