Data mining hinges on one reality about life on the Web: What you do there leaves behind a trail of digital bread crumbs. Companies scoop them up to tailor services, like the matchmaking of eHarmony or the book recommendations of Amazon. Now colleges, eager to get students out the door more efficiently, are awakening to the opportunities of so-called Big Data. Welcome to college, quantified: Data mining produces customized recommendations for courses in which students are likeliest to succeed, and for how they should be taught. The new breed of software can predict how well students will do before they even set foot in the classroom. It recommends courses, Netflix-style, based on students' academic records.