Breaking the Buck - A decline below one dollar in the share amount of a money market fund is the breaking the buck phrase. A money marketfund share amount may break a dollar if a key component decline happens in the value of the securities owned by the fund. For example, a shareholder borrowing may default on commercial paper held by a fund. Federal regulators projected tightening rules for money-market mutual funds that will require them to hold a reserve of assets that easier to sell and to invest only in the highest quality securities. The funds of financial executives are the mainstay.