The pile of cash that billionaires dive into each night just got bigger.
Each uber wealthy person boosted their cash holdings by an average of $60 million over the past year, according to the 2014 Billionaire Census published by Wealth-X and UBS (UBS).
Billionaires don't typically park money in cash unless they're nervous about the market or preparing for a major investment.
And lately the stock market has been shattering all-time records and it's been relatively smooth on the economic front.
Maybe Lehman Brothers is to blame. Memories of the scary Wall Street crash six years ago continue to haunt many investors.
"We can't underestimate the impact of the global financial crisis in making many investors far more risk averse," said Kristina Hooper, U.S. investment strategist at Allianz Global Investors.
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Cash = Nimble investing or rainy day fund: Money in the bank earns virtually nothing. But rock-bottom interest rates hasn't deterred risk-averse investors from hoarding cash.
The Wealth-X and UBS report shows that on average, $600 million, or 19%, of billionaires' assets is sitting in cash.
To put that into perspective, that's enough cash to buy the NBA's Milwaukee Bucks and still have enough left over to purchase 500,000 Apple (AAPL) shares.
But cash gives investors the ability to be nimble when making investments and also something to dive into on a rainy day.
"This increased liquidity signals that many billionaires are keeping their money on the sidelines and waiting for the optimal moment to make further investments," the report said.
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Sign of a market top? Stock market doomsayers are constantly looking for hints of a meltdown.
Should the fact that billionaires are hoarding more cash spook everyday investors? Hooper doesn't think so.
"This trend speaks to the general skepticism about this bull market as opposed to any sign the market has topped," she said.
Related: Investors are getting nervous again
It's not just billionaires: Cash is actually the preferred asset class among most U.S. investors.
A 2013 survey of retail investors and wealthy individuals by the State Street Center for Applied Research shows a whopping 37% of their assets are sitting in cash. That compares with just 35% in stocks and 17% in bonds.
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While the fear of investing may be natural given the 2008 meltdown, the preference for cash could cause problems when people approach retirement.
After all, cash doesn't earn anything, unless it's invested.
"We've seen this with so many investors who remain in cash or lack a commitment to stocks. It could be really problematic in terms of meeting long-term goals," said Hooper.
