(Bloomberg) -- U.S. investors are used to treating money-market mutual funds as the equivalent of a checking account. That is about to change for the riskiest of the funds.

The Securities and Exchange Commission votes today to adopt new rules that will change the way prime money funds price their shares. Instead of a stable price of $1, which means a dollar invested can always be redeemed for $1, prime money funds would have to price their shares in a way that will reveal fluctuations.

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