Manchester United have the biggest transfer losses in Europe in the last decade, according to Swiss-based research institute, CIES Football Observatory.
Since 2012 United have a negative net spend of more than one billion euros, more than rivals Manchester City.
The study revealed that the Red Devils have spent 1.545bn euros on transfers, making 470m euros back in player sales.
Fourteen Premier League clubs are in the top 20.
United broke the Premier League transfer record when they signed Paul Pogba in 2016 for £89.5m and are set to make no return on the midfielder, whose contract expires at the end of the season.
Other costly signings include Anthony Martial (£36m) in 2015 and Donny van de Beek (£40m) in 2020. Both players left on loan in the January transfer window.
Premier League champions City are second in the table with a negative net spend of 984m euros. City have spent 1.699bn euros on players in the past decade but made 715bn in sales.
Paris St-Germain were third with losses of 914m euros and Barcelona fourth with 650m. Arsenal completed the top five with losses of 583m.