Bloomberg -- Wealth among Asia-Pacific millionaires may top North America’s as soon as next year as Japanese economic growth boosts investor returns in the country, a report by Cap Gemini SA and Royal Bank of Canada showed.

Asians with at least $1 million in investable assets are expected to see their riches climb to $15.9 trillion by 2015 from $12 trillion last year, according to the 2013 Asia-Pacific Wealth report, released today. North American high net-worth individuals held $12.7 trillion in 2012.

Japan, the world’s best-performing major stock market this year, accounts for more than half of Asia’s millionaires and will drive regional prosperity as Prime Minister Shinzo Abe’s economic stimulus policies aim to reverse 15 years of deflation, the report showed. The country last year posted a 5.2 percent expansion in millionaire wealth, the slowest among 18 Asian countries tracked in the study.

“Despite its lackluster growth in recent years, Japan remains a strong force in the market,” the report stated. Improved market prospects may encourage rich Japanese “to shift their asset allocation from cash to equities, spurring further wealth growth in mature Asia.”

Asia-Pacific millionaires expanded their assets at an annual rate of 4.9 percent in the five years to 2012, three times faster than expansion in North America, home to the largest concentration of millionaire wealth, according to the report.

The number of high net-worth individuals in the Asia- Pacific region grew 9.4 percent to 3.68 million last year, slipping to second behind North America, which rose 11.5 percent from a year earlier to 3.73 million, according to the 17th annual World Wealth Report published in June.

Asia-Pacific’s slower millionaire population increase last year is expected to be temporary and it will reclaim the top spot as early as 2014, today’s report showed.

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