The world has about 17 million millionaires, as counted in U.S. dollars, and 4 million of them are in China, according to a report released Monday by Boston Consulting Group (BCG). China's numbers are more impressive because a year ago it had about 3 million millionaires. The number of Chinese households with more than $1 million in private cash, stocks, and financial investments (not counting real estate or luxury goods) ballooned mostly because of the 38 percent jump in China's stock market, BCG said. That's true in more than just China, too.