Japan’s Government Pension Investment Fund, the world’s largest manager of retirement savings, posted a record 10.2 percent annual return as stocks surged and a weaker yen boosted the value of overseas assets.

The GPIF held 120.5 trillion yen ($1.2 trillion) of assets as of March 31, boosted by a 29 percent surge in overseas equities and 23 percent gain in Japanese stocks, according to a statement released by the fund today. The total return is the biggest since 2006, when the pension fund was established in its current form by the government.

The pension fund said on June 7 that it’s cutting local bond holdings to buy more stocks and foreign securities, and plans to leave its asset allocations at the new levels until at least March 2015. The shift toward higher-yielding assets comes as the manager prepares to fund retirements in the world’s oldest population.

Overseas bonds returned 18 percent in the year, while domestic bonds yielded 3.7 percent, the statement said.

The Topix index, the country’s broadest equity measure, rose 21 percent in the financial year ended March 31, the best gain since 2010. Benchmark 10-year government bond yields have swung from an all-time low of 0.315 percent to as much as 1 percent since the Bank of Japan announced monetary easing measures in April.

GPIF is the biggest pension fund in the world by assets, followed by Norway’s government pension fund, according to the Towers Watson Global 300 survey in August. The Japan fund didn’t alter the structure of its holdings during the 2008 financial crisis or in response to the 2011 earthquake and nuclear disaster.