JEJU (South Korea) (AFP) - A look at the world golf rankings reveals an astonishing fact - three of the top four, 11 of the top 20 and 41 of the top 100 are from South Korea.

But that's the women.

Finding a Korean in the men's top 100 is a little harder: There are only four.

The best of them is 41st-ranked Kim Si Woo, who at 21 this year became the youngest winner of the Players Championship.

There's a big gap to the rest. An Byeong Hun is 79th, Kang Sung is 80th and Wang Jeung Hun 87th.

It has perplexed golf fans for years: Why does Korea have such a massive gulf between the sexes?

It has also been a talking point at this week's CJ Cup, the United States PGA Tour's first foray into South Korea.

Some believe it is all to do with size.

"The women don't have a decided disadvantage physically," said Kang, who stands 1.73 metres tall, on the PGA Tour's website on Wednesday. "I think we're at a disadvantage to the Americans. We're a little smaller, a little weaker. The Americans are stronger, taller, bigger."

FedExCup champion and PGA Tour player of the year Justin Thomas is one of the longest hitters on tour. He launched a drive 413 yards at the WGC Bridgestone in 2016.

But at 1.78m, Thomas is hardly a giant. He is the same height as four-time Major winner Rory McIlroy, another who belts the ball prodigious distances.

"I've always been a smaller person. I guess I always swung really hard," Thomas said on Wednesday. "I am trying to get a little stronger but it is really just for injury prevention."

If size isn't everything, there must something else contributing - such as military service. South Korean men must serve two years in the armed forces, usually between the ages of 20 and 25.

Women are exempt, and therefore free to continue their golf development.

Bae Sang Moon knows all about it. He returned from the army to professional golf last month having seen his world ranking plummet from 85 to 1,900 in the two years he didn't play.

The CJ Cup will be his third event back. He hasn't made a cut yet.

If military service were compulsory in the US then two of the hottest golfers on the planet, 23-year-olds Thomas and Xander Schauffele, could be in the armed forces now.

British Open champion Jordan Spieth won the first two of his three Majors as a 21-year-old, just around draft time for Koreans.

There's also the Pak Se Ri factor: the impact on the women's game of Korea's first superstar golfer, which cannot be underestimated.

Pak's rookie LPGA Tour season victory in the 1998 US Open - when she was just 20 years old - is still seen as a watershed moment in the women's game.

She was not only the first Korean, but also the first Asian to win the oldest women's Major, and became the poster girl for a South Korean golfing boom that has gone from strength to strength and shows no sign of slowing.

There have been successes for the country's men. The 2009 PGA Championship winner Yang Yong Eun was Asia's first, and to date only, male Major winner.

Choi Kyung Ju is South Korea's most successful player with eight USPGA Tour titles among 22 worldwide victories.

Choi regards this week's CJ Cup as a vital development to help South Korea's men match the women's achievements. And he believes that day might not be too far off.

"In terms of the level of performance I think Korean men are in line with the Korean female players," Choi said.

"A lot of other players are ready to take on the PGA Tour in terms of their physical condition, their mentality, their technique, and this event will give them a push to show them that they can indeed do it.

"I'm quite optimistic and I think that Asian players, including Korean players, will keep knocking on the PGA Tour's door."

The 2013 Masters champion and former world No. 1 Adam Scott went further.

"I think the number of Korean players will double on the PGA Tour in the next five to 10 years," he predicted on Wednesday.

"There are so many Korean professionals playing tours around the world it is for sure going to happen that the number of Korean players is going to increase on the PGA tour."

The Australian added that if practice makes perfect, they are on the right track. "Generally the Korean players practise as much if not twice as much as other players," he said. "They are very hard workers."