Manchester United and Manchester City have both spent over a billion dollars more on buying players than they have on selling - but for one of these clubs it has meant footballing success.

Each of two Premier League giants, Manchester United and Manchester City, have become the most wasteful clubs when it comes to transferring players over the past decade, a new study carried out by the CIES Football Observatory has revealed.

In an effort to regain its past glory, in the last 10 years, Manchester United has spent $1.7 billion to strengthen its squad while it received just $542 million from sales made. The Red Devils have lost $1.22 billion in transfers.

Manchester City is not far behind having invested $1.9 billion in transfers while it sold players worth $749 million over the last decade. The City’s net loss is $1.17 billion.

Unlike Manchester United, Manchester City has won the Premier League five times in the last decade while its city rival has won just one, and that was back in 2012.

French giant Paris St-Germain comes in third with negative net transfer spending over the past decade with its $1.09 billion net loss.

Other European teams are quite far behind these three big clubs.

“Thirteen clubs from the English Premier League in the top 20. All of the current English top division teams have negative net transfer balances, except for freshly promoted Brentford (+$48 million),” the report said.

When it comes to the most positive net transfer spending, two French clubs LOSC Lille and Olympique Lyonnais are at the top of the rankings for Big 5 league teams with the most positive net balances on the transfer market since January 2012.

LOSC Lille has made $391 million net revenue from transfers while Olympique Lyonnais made $257 million.

Three Italian teams specialised in the trading of players follow them: Genoa, Udinese and Atalanta.

Athletic Club stands out among Spanish Liga teams, as well as Hoffenheim in the German Bundesliga.

Although the coronavirus pandemic cut overall transfer spending among European teams, the over-representation of Premier League clubs among those with the most negative net balances for transfers has been noticeable since the pandemic.

“A 58 percent drop was recorded between the last full pre-Covid calendar year (2019) and the first full post-Covid one (2021)” the report noted.

Since the pandemic, there has been a 10 percent decrease in the transfer fee investments for English clubs while it recorded a 74 percent drop for Spanish clubs.

Manchester United (-$249 million) tops the table ahead of five other English teams: Arsenal, Chelsea, Leeds United, Tottenham and Manchester City. 

Juventus with -$159 million transfer spending since the pandemic, comes after six English clubs in the list with most negative net transfer spending after pandemic.

The pandemic has reinforced the domination of English Premier League clubs on the transfer market. 

The percentage of transfer spending of the latter in comparison to the total Big 5 league clubs’ expenditure has increased from 36 percent between January 2012 and January 2020 to over 45 percent for the three post-Covid transfer windows.