The wealthiest Americans are betting on the stock market.

In a potentially encouraging sign for all equity investors, the majority of investors with $5 million or more in net worth (not including homes) plan to invest in equities  -- both individual stocks and stock mutual funds -- during the next 12 months, according to a new survey. The report found that 71% of these investors expressed this intention, compared with just 52% three years ago.

The survey was conducted by Spectrem Group, a consulting firm in Lake Forest, Ill. The results were gathered from 3,000 high-net-worth investors in the fourth quarter of last year, Spectrem said in a statement.

The study also  found that equities are the top investment pick among these investors. Cash-based instruments came in second, with 51% of these wealthy investors planning to invest in them.

“Wealthy investors remain cautious because of the ongoing economic and political uncertainties,” Spectrem Group president George H. Walper said in the statement. “As a result, they are balancing their increased exposure to equities by retaining a sizable amount of cash. Their interest in all types of investments will increase substantially when the uncertainty in Washington around taxes and spending is resolved and unemployment levels are reduced.”

The wealthiest investors are more aggressive than their slightly less wealthy counterparts. Among people with $1 million to $5 million in investible net worth, 55% intend to invest in equities in 2013, versus 45% in 2010, the study found. Still, cash-based instruments will edge out stocks as the top 2013 holding in this group, at 56%.

Those with smaller nest eggs are increasing their stock holdings, but more slowly, according to Spectrem. Only one in three "mass affluent" investors -- those with $100,000 to $1 million in investible net worth -- will invest in equities this year, up from 23% in 2010, the survey found. Equities rank a distant second among 2013 investments for this group, with cash remaining king; 60% plan to put money in short-term instruments.