This is some interesting work that has been summarized in a number of places (Science Daily, Phys.org, Reddit (auto-summarized), Science World Report). In essence, the authors "construct a labor flow network of over 4 million firms across the world' using employment data from LinkedIn. This is used to draw conclusions about the nature of industrial clusters and of economic development. Successful geo-clusters "exhibit a stronger association between the influx of educated workers and financial performance.... Workers tend to change their jobs between geographically close firms with similar skill requirements. This tendency leads to knowledge spillover and innovation, serving as a prominent feedback mechanism in the formation of geo-industrial clusters."