The number of papers indexed in the databases Scopus and Web of Science, for example, has recently been increasing exponentially, at a rate of 5.6 percent per year. By one estimate, researchers around the globe are devoting a collective 15,000 years of work to peer review every year—work that, if paid, would cost $1.5 billion for the share done in the US alone. Increasingly, researchers are finding it hard to donate that kind of time.