The number of millionaire households declined 2.5 percent in the United States last year amid sluggish economic growth and volatile financial markets.

The 2011 total was 5.13 million, compared to 5.26 million a year earlier, according to a report from the Boston Consulting Group (BCG).

The United States still has more millionaire households than any other country, by a huge margin. Japan placed second with 1.59 million, followed by China with 1.43 million.

Editor's Note: You Deserve to Know What Obama and Bernanke Are Hiding From Americans

The United Kingdom, Germany, Switzerland, Italy, Taiwan, Hong Kong, and France fill out the top 10 in that order.

Worldwide, the number of millionaire households gained 175,000 last year, or 1.4 percent, to a total of 12.6 million. The gains were concentrated in China and India.

In the United States, 4.3 percent of all households were worth at least $1 million. That percentage put us in seventh place worldwide, behind Singapore (17.1 percent), Qatar (14.3 percent), Kuwait (11.8 percent), Switzerland (9.5 percent), Hong Kong (8.8 percent), and the United Arab Emirates (5 percent).

When it comes to households worth more than $100 million, the United States led the way with 2,928 last year. The United Kingdom placed second, with 1,125, followed by Germany, Russia, and China.

Looking forward, BCG expects North American wealth to grow at a compound annual rate of 1.8 percent over the next five years, reaching $41.5 trillion by the end of 2016.

Rising stock markets in developed countries should spark that gain, BCG says.

Editor's Note: You Deserve to Know What Obama and Bernanke Are Hiding From Americans