Staša Milojević1, Filippo Radicchi2, John P Walsh3. 1. Center for Complex Networks and Systems Research, School of Informatics, Computing, and Engineering, Indiana University, Bloomington, IN 47408; smilojev@indiana.edu. 2. Center for Complex Networks and Systems Research, School of Informatics, Computing, and Engineering, Indiana University, Bloomington, IN 47408. 3. School of Public Policy, Georgia Institute of Technology, Atlanta, GA 30332.