For an increasing number of South Koreans, being a family man means seeing less of the family than ever before. Many South Korean fathers stay at home and work while they send their wife and children abroad - often for years at a time - for the sake of their children's education. The left-behind fathers have taken on a common nickname - and a common set of problems.

Geum Hee-yeon loves his family. He says that is why for most of the past four years, he has lived more than 10,000 kilometers away from them.

While he stays in South Korea and works, his two teenage children go to school in the United States. His wife takes care of them there.

Geum, the dean of political science at Seoul City University, says he wanted his children to have a U.S. education because he believes the rigidly conformist South Korean school system is inadequate.

"The education they got was how to memorize. Not how to analyze, how to describe, explain. They don't learn to solve a problem logically."

Many other South Korean fathers share Geum's disappointment with the education system here, or they want their children to study abroad to learn another language, particularly English. They have made the same decision to remain behind while they send their families abroad - for anywhere as long as 10 years. These fathers have earned the nickname - "kirogi appa," or "goose dads."

South Koreans say the name derives from the loyalty wild geese show to their mates. Figurines of geese are often given as a gift to couples here, to symbolize marital love and sacrifice.

Choi Yang-sook did post-doctoral research on goose dads at Seoul's Yonsei University. She says the practice is expanding.

She says there are no exact figures, but estimates there are between 30,000 and 50,000 goose dads in South Korea. She says, more important than the exact number is the psychological effect the goose dad trend has.

Geum has felt the psychological effects first hand. He says in Korea, families depend on a father as the hub of a household. But after his family had been in the U.S. for a while, Geum says he started to feel irrelevant.

"My wife, my kids, were doing everything right - without me," he said. "So I thought, oh, I'm just kind of a small part. Just give them money. I kept thinking - do they need me, or not?"

Geum's daughter, Ji-won is a junior at a university in Ohio, but was in Seoul on break recently. She said when she was younger she did not realize the loneliness and worry her father was going through.

She says she often took her father's sacrifice for granted, because it had been her parents' decision to have her study in the United States. She adds, as her younger brother entered adolescence, he began to grow apart from their father because of the distance.

Geum says about a year ago, the anxiety of being a goose dad began to take a physical toll.

"I got sick. Terribly sick. Some kind of stressful panic disorder," he said. "And the doctor said the only way to cure my disease is to let them come back and join me."

Geum says many goose dads deal with the stress of being away from their families by drinking alcohol with each other, which his health problems prevent him from doing.

Instead, his family came back for several months and now that Geum is recovering, they plan to return to the United States soon.

Despite the hardship, goose dads have a better situation than the men Koreans refer to as "penguin dads." As the nicknames imply, goose dads can fly, because they can afford the occasional plane ticket to visit their families. Penguin fathers, who work in lower income jobs, remain grounded - and often go for many years at a time without seeing their wives and children.