That, at least, is how the transfer market usually responds to international tournaments. According to 21st Club, a consultancy, each time a player found the net in the World Cup and European Championship tournaments in 2004-16, his price went up by, on average, 13%. After the 2014 World Cup James Rodríguez, whose six goals for Colombia made him the top scorer, earned a reported €80m move to Real Madrid. That was twice what 21st Club estimated he was worth from his career record.
The club soon realised it had overpaid. Mr Rodríguez struggled, and ended up loaned to Bayern Munich. Indeed 21st Club has found that though a footballer’s goals for his club in the previous season predict his future impact, those at an international tournament do not. That should not be surprising. A World Cup lasts five weeks and features plenty of mismatched teams; a domestic season is eight months of tough games. Mr Mbappé’s four World Cup goals are a less useful indicator than the 47 he scored in his two most recent club seasons.
Could Mr Mbappé net a spectacular transfer? He says he is not thinking of moving and earlier this month Real Madrid denied rumours that it had made a bid. Even so, speculation continues. Bookmakers give the club about a one-in-four chance of luring Mr Mbappé from Paris. Otherwise, the transfer market seems flat. Russia’s Aleksandr Golovin is the only surprise World Cup star close to moving—and his rumoured transfer to Chelsea may owe more to the patriotism of Roman Abramovich, the club’s Russian owner, than to its scouting department.
For most of football’s history, scouts relied on hearsay for foreign transfers. In 1996 Southampton, an English team, signed someone claiming to be the cousin of George Weah, Africa’s biggest star. After his dreadful debut, the club discovered he had barely played professionally. An international tournament at least offered a chance to see potential imports play.
Today’s scouts, however, have access to footage and statistics from every league in the world. Raffaele Poli, the head of CIES Football Observatory, says an influx of staff from financial firms has led to greater interest in big data. In 2012 Arsenal purchased StatDNA, an American analytics firm. Both Bayern Munich and Manchester City have worked with SAP, a software company that provided insights for Germany’s World Cup winners in 2014.
The result, says Mr Poli, is an increasingly rational market. A full 80% of the differences between transfer fees for players can be accounted for by variables that CIES uses in its model, with only a few prices raising eyebrows. It reckoned Cristiano Ronaldo, sold earlier this month by Real Madrid to Juventus for €112m, was worth €103m. Real Madrid could easily bid three times that for Mr Mbappé. But it would probably be overpaying.