Total wealth among millionaire households could more than double over the next decade in 25 major economies, growing from an estimated $92 trillion this year to $202 trillion in 2020.

The study shows the United States and Europe will continue to have the greatest concentrations of wealth, even as emerging markets narrow the gap, and that numerous opportunities for growth in local markets around the U.S. remain.

Focusing on the emerging opportunities for wealth managers to serve the wealthiest customers, the Deloitte study provides estimates of the number of households with net wealth above the $1 million, $5 million and $30 million thresholds across each economy.

"We wanted to go beyond some existing wealth management statistics by looking both into the future and across the globe to forecast how wealth among millionaire households might evolve," says Andrew Freeman, executive director of the Deloitte Center for Financial Services. "Identifying and understanding how different market segments are changing can help formulate growth strategies."

Freeman adds, "Which countries may offer the most promising future and how wealth managers can potentially increase profitability in the next decade are important questions for a wide range of financial institutions. These days it's about a lot more than just a few private banks. Each wealth manager needs to consider their individual footprint and see where it might make sense to capitalize on expected long-term shifts. While there may be enormous growth in the mass affluent sector, many of those customers may also be migrating into the millionaire category."

Among the report's main findings:

• Among emerging markets, Deloitte expects China to continue to be the driving force in the growth of millionaire wealth, followed by Brazil and Russia. Of the 25 countries examined in this study, China and South Korea will join the top 10 countries in terms of the total number of millionaires by 2020.
• While Switzerland may have the highest per capita wealth overall of the countries studied with $4.2 million in 2011, Singapore may rank No. 1 in 2015 and 2020 with $4.5 million and $5.4 million, respectively, in per capita wealth.
• Australia may make an entry into the top 10 in 2020 with 1.6 million millionaire households; the country is also projected to experience the fastest growth rate of the developed economies.
• The wealth of millionaire households in the U.S. could reach $87 trillion in 2020, up from $39 trillion in 2011. In 2020, 43 percent of the world's wealth held by millionaire households is predicted to be in the U.S. While this is only a slight increase from 42 percent presently, the number of millionaire households in the country is projected to increase from an estimated 10.5 million in 2011 to 20.6 million in 2020.
• Among the forecasts for each of the individual 50 U.S. states, California is expected to remain the state with the wealthiest households, while New Jersey will continue to have the greatest density of millionaire households. The East Coast could see the highest growth rates; New York and Florida will together add 1.5 million new millionaire households by 2020.

The 24 economies outside the U.S. included in the report are: Australia, Brazil, Canada, China, France, Germany, Hong Kong, India, Italy, Japan, Malaysia, Mexico, the Netherlands, Norway, Poland, Russia, Singapore, South Korea, Spain, Sweden, Switzerland, Taiwan, Turkey and the United Kingdom.

Wealth in this study includes financial assets (stocks, bonds and other investments) and non-financial assets including primary residence, durables, business ownership and other assets. In order to maximize the reliability of estimates, the analysis relies solely on actual data sources. The study was sponsored by the Deloitte Center for Financial Services and conducted with Oxford Economics.

"It's all about strategy," says Freeman. "Asset and wealth managers looking at the study can draw their own conclusions about how much service will be required in an economy expected to have rapid growth in wealthy households and how much these households might prefer to locate their wealth in, for example, existing international centers of wealth management or private banking."

The report – including more of the methodology and economy-by-economy projections – can be found online at www.deloitte.com/us/globalwealth