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Marks said that makes investing during these times difficult.
"I describe most assets as being priced on the high side of fair. All we can do is pick from among the best that's out there," he noted.
He thinks the better bargains are those that aren't available to the public, including second-tier real estate and European nonperforming loans.
That said, he doesn't think valuations are excessive or "bubbling."
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"Stocks are either a little higher than usual, or not, but they're not in the territory they were in in 2000, for example," Marks said.
The reason for the current market valuations is a combination of the strong demand for financial assets and the Federal Reserve's zero interest rate policy, which "coerced" people to resume investing after the financial crisis, he said.
"By reducing the risk-free rate to zero, people with money have to go out and invest that money in the riskier parts of the curve to actually make any money."