(Bloomberg) -- A hallmark of the $18 trillion mutual-fund industry is that it promises easy entry and exit for investors. U.S. regulators now want new protections to ensure that pledge can be met due to concerns that firms have loaded up on hard-to-sell assets.

The five-member SEC voted unanimously to pass a measure Tuesday that addresses criticisms that its rules haven’t kept pace with the evolution of the fund industry. The SEC’s proposal follows warnings from the Federal Reserve and International Monetary Fund that some funds could struggle to meet investor redemptions during a market rout.

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