Inequality Constraints in the Univariate GARCH Model
单变量 GARCH 模型中的不等式约束
To keep the conditional variances generated by the generalized autoregressive conditional heteroscedastic (p, q) model nonnegative, T. Bollerslev imposed nonnegativity constraints on the parameters of the process. The authors show that these constraints can be substantially weakened and so should not be imposed in estimation. They also provide empirical examples illustrating the importance of relaxing these constraints.