13.51 Flu epidemics and correlation: In 2009, researchers at Google demonstrated that they could detect the spread of flu epidemics in the United States based on the correlation between a set of Google search terms that users were entering and the number of doctor’s visits for the flu (Ginsberg et al., 2009). These data allowed them to detect the spread of the epidemic about one week faster than the Centers for Disease Control and Prevention did. Is this a big data success or a big data failure? Why?