Stationary efficiency of co-evolutionary networks: an inverse voter model Chen-Ping Zhu12, Hui Kong1, Li Li3 Zhi-Ming Gul, Shi-Jie Xiong4Stationary efficiency of co-evolutionary networks: an inverse voter model Chen-Ping Zhu12 ,Hui Kong1 ,Li Li3 , Zhi-Ming Gu1 , Shi-Jie Xiong4