The map was created by looking at the official Twitter accounts for each team, using their followers as an indicator of allegiance. You can discover at a glance which teams dominate each country around the world.
Fans can toggle the map to view specifically their own club's support worldwide; see the most popular clubs overall; and even compare their club with a rival. What's more, by using the 'Zoom to' function you can pinpoint any country around the world instantly.
Original source: Premier League fans show colours on Twitter