The Asia-Pacific region was home to 3.37 million high net-worth individuals, who are defined as having at least $1 million to invest, according to the report by Capgemini and Royal Bank of Canada released Tuesday.
Their numbers were up 1.6 percent from the year before, although their combined wealth shrank 1.1 percent to $10.7 trillion.
North Americans still held the biggest share of world wealth at $11.4 trillion, even though it was down 2.3 percent. But the continent's wealthy population fell to second place as their numbers dipped 1.1 percent to 3.35 million.
Europe, which was overtaken by Asia in 2009, came third with 3.17 millionaires worth $10.1 trillion.
Overall, the combined wealth of the world's 11 million rich declined 1.7 percent in 2011 to $42 trillion. The contraction came as financial markets grew more volatile over widespread concerns about the European sovereign debt crisis.
Markets were also unsettled by a downgrade of the U.S. sovereign credit rating and unrest in Arab countries that kept oil prices high. In Asia, rising inflation, shrinking exports and natural disasters such as Japan's devastating tsunami added to market turbulence.
The world's superrich, defined as worth $30 million or more, took the biggest hit.
The ultrawealthy are more likely to invest their money in higher risk assets such as hedge funds, private equity or commercial real estate.
While returns can be greater, if markets turn sour such investments are also harder to unload for a "palatable price in a viable time frame," so instead they were stuck in superrich investors' portfolios, where they quickly lost value last year, the report said.
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(This version CORRECTS day of release of the report to Tuesday, not Monday.)