[C]itations matter the most, and if you look at the ranking systems, it’s all right there. The Times Higher Education world-university rankings, U.S. News — look at whichever you want, and somewhere between like 30 percent and 60 percent of those rankings are based on citations. Citations are so easy to game. So people are setting up citation cartels: “Yes, we will get all of our other clients to cite you, and nobody will notice because we’re doing it in this algorithmic, mixed-up way.” Eventually, people do notice, but it’s the insistence on citations as the coin of the realm that all of this comes from.