The football transfer market is a big source of news and excitement for fans. Transfermarkt is synonymous with that market. Using crowdsourcing, the Transfermarkt database hosts about 760,000 player profiles, 80,000 coaches, 41,000+ referees, 75,000 clubs, and more than 12,000 agents. What started as a hobby for Matthias Seidel has become football’s largest data community. We had a chat with Thomas Lintz, Managing Director of Transfermarkt.