Japanese corporate and government pension assets managed by investment companies fell 4.5% to ¥79 trillion ($990 billion) last fiscal year as payouts exceeded contributions, said the Japan Pensions Industry Database.

The assets were spread over 5,186 mandates held by 110 firms in the year ended March 31, with foreign managers making up 14 of the top 25 investment companies, according to the industry researcher. BlackRock (BLK) Japan managed the most money with ¥13.8 trillion, followed by Sumitomo Mitsui Trust Bank Holdings and Mizuho Trust & Banking Co., according to the report, which used filings with the Japan Securities Investment Advisers Association.

Japanese pension plans oversee $3.36 trillion, the world's second-largest pool of retirement assets after the U.S., with 98% of them employing defined benefit plans, according to Towers Watson. The funds, which have traditionally invested mainly in bonds, have been expanding their strategies to maintain steady returns and fund retiree benefits as the country faces a shrinking workforce, with 2012 marking the first year the nation's baby boomers are set to retire.