TAIPEI, TAIWAN - As a schoolteacher, Ariel Shen has been observing Taiwan's declining birth rate from up close.

Five years ago, each classroom at her middle school in downtown Taipei had 28 students, but now it has 20, and the trend shows no sign of abating. She is thinking about starting a business, just to stay secure financially.

"My colleagues and I are definitely very concerned," 37-year-old Shen said. "Some have already had to leave for other schools."

Taiwan, with a population of 23 million, now has the dubious distinction of having the lowest birth rate in the world, according to the Population Reference Bureau, a think tank based in Washington DC. Taiwan's interior ministry says just 1.05 children are born per woman, down from 7.04 in 1951 and 2.10 as late as 1984.

"It's not just the lowest level ever in Taiwan, it's the lowest level in history. Nobody has ever gone that low," said Carl Haub, a demographer at the Washington bureau.

The development is a paradox in a society that remains devoted to Chinese tradition, where offspring are considered a blessing and a guarantee that the lineage will continue into the future.

Part of the explanation is economic and reflects the way a child has changed from being an asset in the rural society of half a century ago - an extra pair of hands at the family farm - to a major financial burden.

Rising prices of everything from healthcare to education have made many Taiwanese think twice before they have another child.

"There's also an immeasurable part of it, and no one can quantify this. Young people don't come out of school with the idea that they want to raise a family," said Haub.

"There's a reaction among young women, who see how many children their mothers had, and watched them spend all that time looking after household matters, and that's not necessarily what they want to do."

Weakening family ties consolidate this mindset, as young people migrate from the countryside into the cities, away from the watchful eyes of their parents and grandparents.

This relieves them from pressure from the older generation to produce children, and many instead opt for a materially comfortable single existence.

They are encouraged by modern media that hail the ideal of individual fulfillment, a far cry from the family-oriented tradition, experts said.

The consequences will be felt sooner than many expect, and it will be only a few years before Taiwan starts changing profoundly, they warned.