Tibet's population has grown about 140 percent in five decades, the fastest population growth rate anywhere in China, the regional government said Tuesday.

Tibet had 2.9 million permanent residents at the end of last year compared with 1.228 million in 1959, according to an official document released at a seminar on Tibet's demographics held in the capital city of the Tibet Autonomous Region.

In the last decade, Tibet's population has been growing at a rate of 1 percent per year, higher than the national average of about 0.5 percent.

More than 90 percent of Tibet's permanent residents are Tibetans, according to the last national census, conducted in 2000.

Tibet's fast population growth is because Tibetan families are not subject to the nation's one-child policy.

China's family planning policy limits most families in China's inland to one child.

On the other hand, better medical care and social welfare have also increased Tibetans' average life expectancy, an important index of human development. It has risen to 67 years, from 35.5 years in the 1950s.

The maternal mortality rate has dropped from 50 deaths per 1,000 live births in the early 1950s to 3.1 per 1,000 in 2007 while the infant mortality rate has dropped from 430 deaths per 1,000 to 24.5 per 1,000.

Still, Tibet is facing the challenges of an aging society, the document warned.

More than 200,000 Tibet residents are aged over 60, about 10 percent of the region's population.

Tibet has 134 welfare homes for elderly people in agricultural and pastoral areas but that is not enough to accommodate the region's unprovided for senior citizens, the document said.

At least 2,340 senior citizens in cities and 13,000 in rural areas have neither a pension nor a family for support.

The regional government has invited scholars to research Tibet's demographics and develop strategies for human development on the plateau.