Stock Market Rally Means 400,000 New Millionaires

• Those with $5 million or more in net worth NIPR advanced to 1.14 million from 1.078 million in 2011 and 840,000 in 2008.

• Those with $25 million or more in net worth NIPR grew by 10,000 to 117,000 in 2012 and up from 84,000 in 2008.

While the ranks of investors with at least $100,000 in net worth have finally surpassed the previous 2007 high, the numbers of households at the higher wealth levels are still below their 2007 highs. In general, though, those with more wealth have been better able to weather the downturn because of the diversity of their investments and willingness to stick, in part, with stocks.

"Just as the stock market crash triggered a steep drop in the net worth of wealthy investors, the rebound in equities has made it possible for many affluent households to largely recover," George Walper Jr., president of Spectrem Group, said in a statement. "Wealthy investors who minimized stock ownership in recent years, however, have not seen their assets grow at the same rate."

As a group, wealthy investors with $500,000 up to $1 million showed the greatest reluctance to rely on stocks in recent years and held more of their assets in cash instruments longer than other wealth segments. As a result, that category of investors has the farthest yet to go before reaching its pre-recession total, even compared with those with $100,000 to $500,000 in net worth.