“…Similarly, we also predict the volatilities using four popular HAR-RV-type models, including HAR-RV, HAR-RV-J, HAR-RV-CJ, and HAR-RV-TCJ, which all utilize only high-frequency data. Second, to address the issue of model uncertainty 1 (see, e.g., Avramov, 2002;Becker & Clements, 2008;Rapach, Strauss, & Zhou, 2010;Stock & Watson, 2004), we use a mean combination approach to separately generate the GARCH-class and HAR-RV-type forecasts. This is because the simple mean forecasts cannot be outperformed by other complicated combination forecasts (see, e.g., Claeskens, Magnus, Vasnev, & Wang, 2016;Rapach et al, 2010;Stock & Watson, 2004).…”