The population of millionaires worldwide surged by 9 percent last year, growing to 12 million, according to a report. [1] [2]

The World Wealth Report, from Capgemini and RBC Wealth Management,  said rising stock markets and stronger real estate helped create 1  million new millionaires worldwide. Their wealth surged 10 percent to  $46 trillion—more than the combined gross domestic product of the  European Union, the U.S., China and Japan. (The report defined  millionaires as individuals with $1 million or more in investable  assets.)

“Overall, we saw strong equities, stronger real estate  markets, and a bottoming out of the economies in the developed markets,”  said William Sullivan, global head of financial services for Capgemini.  “All of those factors were able to drive growth.”

The report  also highlighted the strength of U.S. wealth creation relative to the  rest of the world, especially emerging markets. North America reclaimed  its position in 2012 as the region with the most millionaires — 3.73 million — a  year after Asia-Pacific took over the top spot for the first time.

(Read More: Key to Getting Rich: Work, Risk or Luck?)

Capgemini said it expects the switch is  temporary and Asia-Pacific, which had 3.68 million millionaires in 2012,  will regain its top spot in the next year or two.  Still, Sullivan said, weakness in Asia—especially China—has led many  companies to lower their previous forecasts for wealth creation  for the region.

“I think it’s been tempered a little,” he  said. “It may not be the astronomical growth predicted.” Still, he said  the domestic markets in Asia are so strong that the region will see  strong millionaire growth in the coming years.

(Read More: We’re Rich Again! So Why Don’t We Feel It?)

The world’s millionaires remain fairly cautious when it comes to  investing. U.S. millionaires have one fifth of their investments in  cash, while Japanese millionaires have half of their portfolio in cash,  Sullivan said.

In North America, about a third of millionaires  are focused on wealth preservation, while 28 percent were focused on  growing their wealth.