HELSINKI (Reuters) - Two percent of adults have more than half of the world's wealth, including property and financial assets, according to a study by the U.N. development research institute published on Tuesday.

While global income is distributed unequally, the spread of wealth is even more skewed, the study by the World Institute for Development Economics Research of the U.N. University said.

"Wealth is heavily concentrated in North America, Europe and high income Asia-Pacific countries. People in these countries collectively hold almost 90 percent of total world wealth," the survey showed.

The Helsinki-based institute said its study was the first global research on the topic, for which there is only limited data.

"We've estimated that the richest 2 percent of adults own more than half of global wealth, while the bottom half own 1 percent," said institute director Anthony Shorrocks.

He likened the situation to that where, in a group of 10 people, one person has $99, while the remaining nine share $1.

"If you think income has been distributed unequally, wealth has been distributed even more unequally," Shorrocks said.

According to the study, in 2000 a couple needed capital of $1 million to be among the top 1 percent on the wealth list -- the richest 37 million people in the world.

More than one in every two of those people lives in the United States or Japan.

And it found that net assets of $2,200 per adult would put a household in the top half of the world wealth distribution.

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