Abu Dhabi Investment Authority, believed to be the world's largest wealth fund, on Monday revealed for the first time the distribution of its assets estimated at around 500 billion dollars.

ADIA, in its first ever annual review, said it invests between 60 percent and 85 percent of its holdings in North America and Europe and between 25 percent and 45 percent in Asia and emerging markets.

The report, which was issued as part of moves towards increased transparency, however, did not reveal the actual size of ADIA assets, which some reports put as high as 800 billion dollars.

Between 46 percent and 65 percent of ADIA assets are held in developed equities, emerging market equities and to a lesser extent in small cap equities, it said.

Ten to 20 percent are invested in government bonds, five percent to 10 percent in hedge funds and managed funds, and up to 10 percent is held in cash, the report said.

Established in 1976 to manage excess oil wealth of the emirate of Abu Dhabi, ADIA's rate of return averaged an annual eight percent over the past 30 years and 6.5 percent per annum during the past 20 years, it said.

A report by the United Nations Conference on Trade and Development last year said ADIA was severely impacted by the global financial crisis, shedding 183 billion dollars of its assets in 2008 alone.

The UN report estimated the value of ADIA assets at 329 billion dollars at the end of 2008, but as oil prices recovered and investments worldwide regained value, the fund's assets are also expected to have gained last year.