NEW YORK (CNN/Money) – There are more millionaire households in 2004 than ever, and they have increased in number at a record rate year-over-year.

MILLIONAIRES IN THE MAKING • He's the boss ... • Living a little, learning a lot

Those are the key findings of the latest Affluent Market Research Program, an annual survey conducted by market information company TNS, which began surveying affluent households in 1981.

TNS found that there are now a record 8.2 million U.S. households with a net worth of more than $1 million, excluding primary residences. That's a 33 percent increase over the 6.2 million households that met that criteria in 2003.

Half of those surveyed are retired.

The number of millionaire households represents about 7 percent of all U.S. households.

The reason for the record growth in millionaires next door? A steady hand in investing throughout the bear market.

"They were still investing in the market. They weren't running," said Jeanette Luhr, manager of the Affluent Market Research Program for TNS who compared this year's data with data as far back as 2000, when the stock market began its precipitous fall.

What's more, Luhr noted, while she saw some increase in bond holdings and a decline in the value of wealthier households' investments during the bear market, there were no wild shifts or swings.

When asked, 48 percent of those surveyed reported little change in their investing approach since the market's collapse, while 46 percent took a "wait-and-see" approach, making few changes to their holdings.

"The average investor may have exited the market post 9/11, but these households simply stayed the course, letting their investments regain value over time. This strategy is starting to pay off," Luhr said in a statement. "Some investment losses were offset by gains in real estate, but for the most part, ownership of stocks and bonds remained fairly stable."

In 2003, the primary cause for growth in millionaire households (13 percent over 2002) was attributed to real estate investments.