Lower rates aren’t sparking demand for low-grade bonds and billionaire investor Ray Dalio knows why.

With yields so low, “the transmission of the monetary policy mechanism will be less effective,” said Ray Dalio, the U.S. hedge fund manager who runs the $160 billion Bridgewater Associates. “We have a deflationary set of circumstances,” which makes it appealing to just stuff your money under a mattress, he said at a panel discussion in Davos, Switzerland, this week.