How can you tell if an algorithm is any good? For University of Michigan assistant professor of information and public policy Ben Green, the answer lies less in accuracy scores, fairness metrics or any other technical measure than in what the system actually does once it’s out in the world. In his new book, Algorithmic Realism: Data Science Practices to Promote Social Justice (MIT Press), he offers data scientists a method for scoping, building and evaluating algorithms in the service of social justice.