With interest rates falling so low, it will soon cost more for fund companies to run somemoney market funds than their investments, The Wall Street Journal reports. Rather than step in to make investors whole or permit their funds to break the buck, some money funds will likely close.

The average yield on a money market fund is now 0.94%, versus 4.16% a year ago, according to iMoneyNet. That is causing a serious problem for many money market funds, since the average money market fund charges 70 basis points in annual fees. Between the yield and the fee, investors are losing money. And—there are 206 funds, some whose prospectus requires them to only invest in Treasuries or other currently low-paying instruments, that are yielding a miserable nine basis points.

If the Federal Reserve moves the key fed funds rate to 50 basis point, the number of funds likely to close will increase much more.

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