“…• GARCHs As for agents, the existing relevant literature mostly focused on four types of agents in the ETS system: the government (i.e., the ETS designer), enterprises (the ETS targets), third parties (the ETS regulators) and ETS market (the ETS platform). As for quantitative models, prevailing models for ETS research fall into six categories by quantification and solution: optimization models (game models [27,33], data envelopment analysis (DEA) [73][74][75], and other linear or nonlinear programming models [46,76]), simulation models (e.g., computable general equilibrium (CGE) [17][18][19], agent-based models (ABM) [1,5] and system dynamic (SD) models [25,48]), assessment models (e.g., analytic hierarchy process (AHP) [77][78][79], technique for order preference by similarity to an ideal solution (TOPSIS) method [80][81][82]), statistical models (e.g., difference in difference [83][84][85], GARCH processes [45,69], vector autoregressive (VAR) models [51,64]), AIs (e.g., artificial neural network (ANN) [54] decision tree (DT) [86][87], support vector machine (SVM) [26,44]) and ensemble models (e.g., AI-based optimization models [44,87], combined statistical and AI models [44,83] and decomposition and ensemble models [54]). Fig.…”