“…We chose the GARCH-MIDAS framework as our research method for two reasons. First, the main goal of this paper is to study whether exogenous variables of monthly sampling frequency can provide effective information for predicting daily volatility And a large number of works have confirmed that the GARCH-MIDAS framework has the ability to reasonably construct a model of mixed-frequency data when matching such low-frequency variables (such as weekly, monthly, and quarterly) with high-frequency daily fluctuation indicators of asset prices ( Wang, Wu, et al, 2022 ; Zhang, Wang, et al, 2022 ). If the high-frequency information of daily prices is transformed into monthly comprehensive information, then a large amount of effective information will be lost, which will also bias the parameter estimation and model prediction ( Engle et al, 2013 ; Engle & Rangel, 2008 ).…”