Serena leads Forbes' female highest earners list, again

This may not be news for the most knowledgeable fan, but there is big, big money in tennis. According to Forbes, the highest-earning female athletes in the world are swinging tennis racquets.

Serena Williams leads the list with annual earnings of $29.2 million ($25 million of that comes from off the court).

World No. 2 Naomi Osaka is closely behind with $24.3 million ($16 million of which are earned off the court). The 21-year-old is the fourth female athlete to earn over $20 million, joining Serena, Maria Sharapova and Li Na.

The list includes Angelique Kerber ($11.8 million), Simona Halep ($10 million), Sloane Stephens ($9.6 million), Caroline Wozniacki ($7.5 million), Sharapova ($7 million), Karolina Pliskova ($6 million), Elina Svitolina ($6 million), Venus Williams ($5.9 million) and Garbine Muguruza ($5.9 million).

Sharapova was on top of the Forbes list as the highest-paid female athlete for 11 years, but has fallen down to No. 7. She's still doing just fine, obviously.

Serena has had a grip on the top spot for the last four years. While the first 10 athletes on the list are all tennis players, golfers, badminton players and soccer stars emerge in the next five spots, along with Madison Keys at No. 13.