BEIJING -- China's social insurance fund had a surplus of 650.8 billion yuan (about $99 billion) in 2016, the Ministry of Finance said in a final accounts report Tuesday.

The surplus brought the total balance of the fund to 6.54 trillion yuan at the end of last year.

Total revenue of the fund rose 8.1 percent year on year to 5.01 trillion yuan, while expenditure rose 11.5 percent to 4.36 trillion yuan.

About 73 percent of revenue came from insurance premiums and another 22 percent was from government subsidies. The remainder could come from interest payments, investment returns or donations.

The faster growth of expenditure over revenue reflects the pressure of an aging population. The share of people 60 years old or above stood at 16.7 percent of the total population at the end of last year, and has been rising fast for years.

China's social insurance fund covers basic old-age, basic medical care, work-related injury, unemployment and maternity.