How many millionaires do you know? The answer to this probably depends on your occupation, location, and whether or not you have your own reality show. But as explained in an earlier post, there are quite a few millionaires in the U.S. -- there will be 10.5 million in 2011 according to the Deloitte Center for Financial Services. That might not sound like too many, but this number is expressed in households, not individuals. And there are only about 118 million households in the U.S. So really, a fairly large -- if not surprisingly large -- portion of U.S. households belong to the millionaire club.

In 2011, using the Deloitte estimate, around 9% of all U.S. households will be millionaires, if you estimate that households will grow this year at approximately the same rate they did in 2009 and 2010. Using millionaire estimates from the recent Deloitte report and the number of households according to the Census Bureau, here's how that percentage has changed over the past decade:

millionaire density 2011-05.png

You can see that millionaires were particularly plentiful when the housing bubble was fully inflated. A lot of wealth was lost when the real estate and the stock markets both crashed. The economy's 2008 collapse cut the percentage of millionaires in the U.S. by more than 3%. But the millionaires are rising again. Since that plummet, the percentage has risen about by 1.2%.

When you think about it, 9% is a pretty large portion of the U.S. to be millionaires. That means nearly 1 in every 10 Americans is a millionaire. So on average, if you drive by 10 cars on the road, one of them is probably a millionaire. Now you know why you see so many Range Rovers, Bentleys, and Ferraris.

But of course, reality is a little more complicated than this approximation. Millionaires are often clumped in certain locations, like major cities in New York, California, Florida, D.C., Massachusetts, Connecticut, and New Jersey. In fact, the Deloitte report predicts that New Jersey will have the highest density of millionaires of any state in the nation by 2020 -- nearly one in every four households. So don't expect reality shows to shun the state anytime soon!