How Visas Shape the Geopolitical Architecture of the Planet
▻https://www.technologyreview.com/s/600750/how-visas-shape-the-geopolitical-architecture-of-the-planet
▻https://d267cvn3rvuq91.cloudfront.net/i/images/img0114.jpg?sw=590&cx=0&cy=34&cw=1844&ch=1037
Saeedian and co begin by creating a network based on the visa policy of all 222 of the world’s nations. In this network, a link exists between two countries if they both allow visa-free travel for their citizens. For example, in this network, there is a link between the U.S. and Canada but not between the U.S. and Mexico.
source article with the (quite ugly) map:
▻http://arxiv.org/abs/1601.06314