Bilevel decision via variational inequalities

In this paper, we introduce the group decision problems in a bilevel programming structure, and its corresponding optimization with equilibrium constraints (MPEC for short) problems. For these models, we establish new existence results, which extend some known results to infinite-dimensional space setting. We also establish the links between group decision problems in a bilevel programming structure and its corresponding MPEC problems in Banach spaces. An interesting example about the mean-variance portfolio optimization is given and the existence and uniqueness results for its corresponding MPEC problems are obtained.