Studies of human mobility usually focus on either the small scale — individuals’ daily commutes — or the very large scale, such as using air-travel patterns to track the spread of epidemics over time. The large-scale studies, now made possible by vast data generated and collected by technologies like sensors and cellphones, are very good at describing the big picture, but don’t provide detail at the individual level. Smaller-scale studies have the opposite characteristic: their findings generally can’t be scaled up from the individual to populations. But a new study by CEE Professor Marta González and postdoctoral associate Christian Schneider bridges that gap. It uses big data and the methodologies of statistical physics and network theory to describe the daily travel behavior of individuals, behavior that holds true at the larger scale of the entire population of two cities on different continents. Read a news story.