The overnight rate stood at 2 percent in March 2002.
The overnight rate had already been slipping in the last few weeks.
The overnight rate had been averaging about 6.75 percent since May.
Most central banks will announce the overnight rate once a month.
The overnight rate is the amount paid to the bank lending the funds.
The central bank's overnight lending rate is already at a four-year high of 25.5 percent.
Investors appear to assume that the overnight rate will be about 3.75 percent by the end of this year.
The overnight rate of 5.25 percent has been the same since the Fed began its "pause" almost a year ago.
The overnight Federal funds rate, meanwhile, was trading at around 7.50 percent, as it did a day earlier.
The overnight Federal funds rate, meanwhile, traded at around 8.30 percent.
