It was established earlier this year that tennis stars Naomi Osaka and Serena Williams are the only two women in the top-100 highest-paid athletes in the world.The pair featured in Sportico’s ranking, which listed basketball icon LeBron James as the highest earning athlete.Osaka, who has equity in more than a dozen brands and endorsement deals with Nissan, Tag Heuer and Louis Vuitton, was ranked 20th.Williams, who owns a venture capital firm and has long-standing partnerships with Pepsi, Gatorade and Aston Martin, was 52nd on the list.A new study from SportsPro, using data from Forbes, has now compared the disparity between the top five highest-paid male and female athletes.In SportsPro’s list, Paris Saint-Germain star Lionel Messi was named as the highest earner, making $130 million (£108 million) over the past 12 months.This is in comparison to the $59.2m (£49.3m) earned by Osaka, meaning there is a 119.6 percentage increase between her pay and Messi’s.

The second highest-paid male athlete is James, who took home $121.2m (£101m). This is a 167.6 percentage increase on the $45.3m (£37.7m) earned by the second highest-paid female athlete, Williams.

Unfortunately, the percentage increase between the highest-paid male and female athletes gets greater as SportsPro moves down the list.

There is a 917.7 percentage increase between the third highest-paid male and female athletes – Manchester United’s Cristiano Ronaldo and Venus Williams.

Ronaldo earned $115m (£95.8m) over the past 12 months, while Williams received $11.3m (£9.4m).

The fourth highest-paid male and female athletes are footballer Neymar and four-time Olympic gymnastics champion Simone Biles.

Tennis star Naomi Osaka

Neymar earned $95m (£79.1m) and Biles $10.1m (£8.4m), giving a percentage increase of 840.6%.

The greatest percentage increase – 954.5 percent – is between basketball star Steph Curry and tennis player Garbiñe Muguruza, who are the fifth highest-paid male and female athletes.

Curry made $92.8m (£77.3m), while Muguruza, winner of the lucrative WTA Finals, earned $8.8m (£7.3m).

It is significant that the majority of female athletes in the highest-paid list are tennis players – the sport arguably has more gender parity than any other, with Grand Slams giving equal exposure to male and female stars.