1. National School of Development, Room 310, Yiyuan Building, Peking University, Beijing, 100871, China. email: liangmei@nsd.pku.edu.cn
2. Research Center for Technological Innovation, Room 378, Weilun Building, School of Economics and Management, Tsinghua University, Beijing, 100084, China. email: innovatormeiliang@gmail.com
3. School of Economics and Management, Room 806, Siyuan East Building, Beijing Jiaotong University, Beijing, 100044, China. email: nnzhang@bjtu.edu.cn