BEIJING - China's social security fund manager on Friday said its investment return for 2015 was 15.1 percent, up from 11.4 percent in 2014 despite downward pressure on the economy.

The National Council for the Social Security Fund earned 228.7 billion yuan ($35.1 billion) from all investment last year, according to a statement on its website.

The rate of return outperformed the average return of 8.4 percent, for the period from the fund's establishment in 2000 to 2014.

The fund is designed to serve as a solution to the country's aging problem, as well as a strategic reserve to support future social security expenditure.

The fund is invested in a variety of financial products both at home and abroad including fixed-income assets and stocks.

By the end of 2015, it had managed assets totaling 1.9 trillion yuan, up from 1.5 trillion yuan a year earlier.

The fund manager vowed to improve the management on investments and raise more money this year to ensure the fund continues to appreciate.