It wasn't a bad year for the world as a whole either. It added 2.6 million millionaire households, a 19 percent increase, to 16.3 million households, according to the report.

The report defines wealth as investible assets. Stocks played the biggest role in driving wealth higher last year, the report said.

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The United States has the highest total of millionaire households in the world. China is second with 2.38 million, followed by Japan with 1.24 million, the United Kingdom with 513,000 and Switzerland with 435,000.

A total of 5.9 percent of U.S. households are now millionaires, compared to 1.1 percent for the world as a whole.

The U.S. percentage is tied for sixth in the world with Bahrain. Qatar is first with 17.5 percent, followed by Switzerland with 12.7 percent, Singapore with 10 percent, Hong Kong with 9.6 percent and Kuwait with 9 percent.

Meanwhile, the Federal Reserve reported last week that U.S. household wealth rose 1.9 percent in the first quarter from the fourth quarter, to a record high of $81.8 trillion, boosted by gains in jobs, home prices and stocks.

"The deleveraging on the consumer front has largely run its course, and we’ve obviously been helped by the run-up in financial assets," Omair Sharif, a U.S. economist at RBS Securities, told Bloomberg.

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