There are more millionaires than ever, and their numbers are growing. According to the Fed’s Survey of Consumer Finances, households with a net worth of $1 million to $3 million grew by 19% from 2001 to 2004 to 8.2 million households, or 7.6% of all U.S. households. (Household net worth is defined as total assets, including primary residence,minus total liabilities, including mortgages.) The only group outpacing new millionaires is up-and-coming millionaires: Households with a net worth between $500,000 and $1 million grew 23% during the same period to 10.4 million, or 9.7% of all households.

Rising real estate has helped lift the fortunes of all homeowners, but there’s more to the rise in net worth than home prices. Economists say a vibrant knowledge economy, flexible capital markets, and an increased emphasis on education from outperforming households have led to a thriving affluent middle-class.