Yin Weimin, minister of human resources and social security, speaks at a news conference of the 19th National Congress of the Communist Party of China in Beijing, Oct 22, 2017. [Photo by Edmond Tang/China Daily]

China is facing challenges to include all people into the endowment insurance system and to keep the development of the endowment insurance fund sustainable, the country's top human resources and social security official said on Sunday.

About 900 million people in China, or 90 percent of the country's population excluding pre-school children and students, have been included into the endowment insurance system, Yin Weimin, minister of human resources and social security, told a news conference on the sidelines of the 19th National Congress of the Communist Party of China.

It's a great achievement, but it's a challenge to include the rest 10 percent into the system, he said.

Yin said the remaining 100 million people are mainly those with flexible employment, those employed in new forms of industry, including internet and express delivery industries, and those employed by middle and small-sized enterprises, most of whom are migrant workers.

In the 1990s, five employed were supporting one retired who were covered by the endowment insurance. Currently, the old-age dependency ratio stands at 2.8:1. The situation will worsen as the country's population continues to age, he said.

People over 60 years old in the country had reached 230 million, or 16.7 percent of the country's total, by the end of last year and those older than 65 numbered 150 million, or 10.8 of the total, according to Yin.

He said China has taken a series of measures to counter the situation, including putting endowment insurance into investment and allocating State-owned property to enrich the fund.