Seoul, South Korea, Nov. 25 -- Yoo Young Yi's grandmother gave birth to six children. Her mother birthed two. Yoo doesn't want any.

"My husband and I like babies so much . but there are things that we'd have to sacrifice if we raised kids," said Yoo, a 30-year-old Seoul financial company employee. "So it's become a matter of choice between two things, and we've agreed to focus more on ourselves."

There are many like Yoo in South Korea who have chosen either not to have children or not to marry. Other advanced countries have similar trends, but South Korea's demographic crisis is much worse.

South Korea's statistics agency announced in September that the total fertility rate - the average number of babies born to each woman in their rep...