How can peer review be effective when the underlying data cannot be shared? When scientists publish their research, they also make the underlying data available so the results can be verified by other scientists. At least that is how the system is supposed to work. But lately social scientists have come up against an exception that is, true to its name, huge. It is “big data,” the vast sets of information gathered by researchers at companies like Facebook, Google and Microsoft from patterns of cellphone calls, text messages and Internet clicks by millions of users around the world.