(CNN) They're the wheelers and dealers, the people that make football transfers happen -- and they're in a lucrative business.

A report released by world governing body FIFA has revealed that intermediaries or agents have been paid a total of $548 million so far this year across 3,844 international transfers. Since 2013, agents have picked up a total of $2.14 billion.

The report analyzed data from all global football transfers in the past five years, comparing instances when players and clubs had used an agent for a move to take place.

Close to 20% of international transfers in this five-year period involved an agent, with individual players more likely to use them than clubs.

Mendes represents Juventus' Cristiano Ronaldo, Raiola works with Manchester United's Paul Pogba while Barnett is the agent of Real Madrid's Gareth Bale.

Raiola has said he is friends with "99%" of his clients and goes as far as to call Pogba "family.

"We just want the player to finish his career with the money he earned, and more -- but not less," he said in an interview with the FT

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In terms of countries, Italian clubs most commonly relied on agents for incoming players in 2018 with over 45% of the country's 175 transfers involving intermediaries.

England was second, although agents that were employed by English clubs were the highest-earning, accruing a total of $155.8 million so far this year.

Agents connected with European clubs accounted for 96% of the money paid to intermediaries in 2018.

When transfer fees have been higher, agents have tended to earn less money from the transaction; between 2013 and 2018, they took an average of 28% of the transfer fee when it was less that $1 million, but this figure was as low as 7.3% for transfer fees over $5 million.

Currently, anyone is able to act as an agent on behalf of a player, but it has been reported that FIFA is planning to reintroduce exams for agents, which were previously ditched in 2015.

The aim is to add greater transparency to transfers, preventing agents from exploiting clubs and players.

"These increasingly larger transactions are often not done in a clean, open manner and raise a lot of questions about potential misuse of funds," said FIFA president Gianni Infantino earlier this year.

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Some English Premier League owners have called for a ban on agent payments following "dual representation" -- whereby an agent is paid by a player and a club for the same transfer.

"They are starting to run football. They are certainly sucking tons of money out of football," West Ham owner David Gold recently said

"We are all trying to pay less, they are doing nothing for football. I can't believe it is even a discussion. Other than agents, everybody else is against them."

London-based agent Michael Di Stefano, an intermediary registered with the FA, has defended the influence agents have in football.

"Players do need more often than not someone to help with the admin stuff," he tells CNN Sport. "Not everyone has the words or know-how to be comfortable when talking money, contracts and obligations."

"If Gianni [Infantino] wants to really set an example, he will cap the fee to a maximum of £1M ($1.26M), no matter how high the transfer fee, and for all those lower, cap it at 5% [of the transfer].

"He could also take away dual representation, forcing the club to represent itself via a club secretary, for example.

"You cannot take the agent out of the game, it's ridiculous to even suggest that. We are just people working (oftentimes for free) and offering fair advice about what is a nasty industry filled with inept, inadequate people at all levels, from the bottom to the very top!"

Danish footballers are most likely to use agents to facilitate transfers, with close to 48% of players this year relying on an agent. This was followed by Norweigan, Dutch, Czech, and Australian players.

The Association of Football Agents has yet to comment on FIFA's report.