NEW YORK (TheStreet) -- Just over one-third of the portfolio of a high-net-worth individual in North America is invested in stocks, even though the S&P 500 is up almost 210% since its March 2009 low, according to a new study.

Defining "high net worth" as those with at least $1 million in investable assets, not including a primary residence, the 2015 World Wealth Report from RBC Wealth Management and Capgemini found wealthy individuals directed 24% of their portfolios toward cash. Some 18% of their portfolio was invested in fixed income, and 12% was allocated toward alternative investments.

"One of the findings we've seen during the last few years when we've done this study is that we see high levels of cash for high-net-worth individuals,' said Bill Sullivan, head of market intelligence at Capgemini Financial Services. "They're using that cash for lifestyle needs and to protect against markets volatility."

Millionaires kept just over a quarter of their portfolio invested overseas.

"They are diversifying across asset classes, but also across regions, as well," Sullivan said.

The report said almost 11% of millionaires' portfolio was invested in Europe.

The survey also said the population of high-net-worth individuals in North America rose 8.6% in 2014 to 4.4 million, compare with a 16.6% increase in 2013. The Asia-Pacific region has 4.69 million high-net-worth individuals, the study said.

RBC Wealth Management is a division of Royal Bank of Canada (RY) - Get Report.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.