In the United States, the federal funds rate is the interest rate at which depository institutions (banks and credit unions) lend reserve balances to other depository institutions overnight on an uncollateralized basis. Reserve balances are amounts held at the Federal Reserve to maintain depository institutions' reserve requirements. Institutions with surplus balances in their accounts lend those balances to institutions in need of larger balances. The federal funds rate is an important benchmark in financial markets.
The interest rate that the borrowing bank pays to the lending bank to borrow the funds is negotiated between the two banks, and the weighted average of this rate across all such transactions is the federal funds effective rate.
The federal funds target rate is determined by a meeting of the members of the Federal Open Market Committee which normally occurs eight times a year about seven weeks apart. The committee may also hold additional meetings and implement target rate changes outside of its normal schedule.
The Federal Reserve uses open market operations to make the federal funds effective rate follow the federal funds target rate. The target rate is chosen in part to influence the money supply in the U.S. economy.
Financial institutions are obligated by law to maintain certain levels of reserves, either as reserves with the Fed or as vault cash. The level of these reserves is determined by the outstanding assets and liabilities of each depository institution, as well as by the Fed itself, but is typically 10% of the total value of the bank's demand accounts (depending on bank size). For transaction deposits of size $9.3 million to $43.9 million (checking accounts, NOWs, and other deposits that can be used to make payments) the reserve requirement in 2007–2008 was 3 percent of the end-of-the-day daily average amount held over a two-week period. Transaction deposits over $43.9 million held at the same depository institution carried a 10 percent reserve requirement.
For example, assume a particular U.S. depository institution, in the normal course of business, issues a loan. This dispenses money and decreases the ratio of bank reserves to money loaned. If its reserve ratio drops below the legally required minimum, it must add to its reserves to remain compliant with Federal Reserve regulations. The bank can borrow the requisite funds from another bank that has a surplus in its account with the Fed. The interest rate that the borrowing bank pays to the lending bank to borrow the funds is negotiated between the two banks, and the weighted average of this rate across all such transactions is the federal funds effective rate.
The federal funds target rate is set by the governors of the Federal Reserve, which they enforce by open market operations and adjustments in the interest rate on reserves. The target rate is almost always what is meant by the media referring to the Federal Reserve "changing interest rates." The actual federal funds rate generally lies within a range of that target rate, as the Federal Reserve cannot set an exact value through open market operations.
Another way banks can borrow funds to keep up their required reserves is by taking a loan from the Federal Reserve itself at the discount window. These loans are subject to audit by the Fed, and the discount rate is usually higher than the federal funds rate. Confusion between these two kinds of loans often leads to confusion between the federal funds rate and the discount rate. Another difference is that while the Fed cannot set an exact federal funds rate, it does set the specific discount rate.
The federal funds rate target is decided by the governors at Federal Open Market Committee (FOMC) meetings. The FOMC members will either increase, decrease, or leave the rate unchanged depending on the meeting's agenda and the economic conditions of the U.S. It is possible to infer the market expectations of the FOMC decisions at future meetings from the Chicago Board of Trade (CBOT) Fed Funds futures contracts, and these probabilities are widely reported in the financial media.
Interbank borrowing is essentially a way for banks to quickly raise money. For example, a bank may want to finance a major industrial effort but may not have the time to wait for deposits or interest (on loan payments) to come in. In such cases the bank will quickly raise this amount from other banks at an interest rate equal to or higher than the Federal funds rate.
Raising the federal funds rate will dissuade banks from taking out such inter-bank loans, which in turn will make cash that much harder to procure. Conversely, dropping the interest rates will encourage banks to borrow money and therefore invest more freely. This interest rate is used as a regulatory tool to control how freely the U.S. economy operates.
By setting a higher discount rate the Federal Bank discourages banks from requisitioning funds from the Federal Bank, yet positions itself as a lender of last resort.
Though the London Interbank Offered Rate (LIBOR) and the federal funds rate are concerned with the same action, i.e. interbank loans, they are distinct from one another, as follows:
Considering the wide impact a change in the federal funds rate can have on the value of the dollar and the amount of lending going to new economic activity, the Federal Reserve is closely watched by the market. The prices of Option contracts on fed funds futures (traded on the Chicago Board of Trade) can be used to infer the market's expectations of future Fed policy changes. Based on CME Group 30-Day Fed Fund futures prices, which have long been used to express the market's views on the likelihood of changes in U.S. monetary policy, the CME Group FedWatch tool allows market participants to view the probability of an upcoming Fed Rate hike. One set of such implied probabilities is published by the Cleveland Fed.
As of 30 October 2019[update] the target range for the Federal Funds Rate is 1.50–1.75%. This reduction represented the third of the current sequence of rate decreases: the first occurred in July 2019. As of March 15, 2020 the target range for Federal Funds Rate is 0 to 0.25 percent, a full percentage point drop less than two weeks after being lowered to 1 to 1.25 percent. 
The last full cycle of rate increases occurred between June 2004 and June 2006 as rates steadily rose from 1.00% to 5.25%. The target rate remained at 5.25% for over a year, until the Federal Reserve began lowering rates in September 2007. The last cycle of easing monetary policy through the rate was conducted from September 2007 to December 2008 as the target rate fell from 5.25% to a range of 0.00–0.25%. Between December 2008 and December 2015 the target rate remained at 0.00–0.25%, the lowest rate in the Federal Reserve's history, as a reaction to the Financial crisis of 2007–2008 and its aftermath. According to Jack A. Ablin, chief investment officer at Harris Private Bank, one reason for this unprecedented move of having a range, rather than a specific rate, was because a rate of 0% could have had problematic implications for money market funds, whose fees could then outpace yields.
When the Federal Open Market Committee wishes to reduce interest rates they will increase the supply of money by buying government securities. When additional supply is added and everything else remains constant, the price of borrowed funds – the federal funds rate – falls. Conversely, when the Committee wishes to increase the federal funds rate, they will instruct the Desk Manager to sell government securities, thereby taking the money they earn on the proceeds of those sales out of circulation and reducing the money supply. When supply is taken away and everything else remains constant, the interest rate will normally rise.
The Federal Reserve has responded to a potential slow-down by lowering the target federal funds rate during recessions and other periods of lower growth. In fact, the Committee's lowering has recently predated recessions, in order to stimulate the economy and cushion the fall. Reducing the federal funds rate makes money cheaper, allowing an influx of credit into the economy through all types of loans.
The charts linked below show the relation between S&P 500 and interest rates.
Bill Gross of PIMCO suggested that in the prior 15 years ending in 2007, in each instance where the fed funds rate was higher than the nominal GDP growth rate, assets such as stocks and housing fell.
A low federal funds rate makes investments in developing countries such as China or Mexico more attractive. A high federal funds rate makes investments outside the United States less attractive. The long period of a very low federal funds rate from 2009 forward resulted in an increase in investment in developing countries. As the United States began to return to a higher rate in the end of 2015 investments in the United States became more attractive and the rate of investment in developing countries began to fall. The rate also affects the value of currency, a higher rate increasing the value of the U.S. dollar and decreasing the value of currencies such as the Mexican peso.
Rising interest rates in the United States are driving money out of many developing countries, straining governments and pinching consumers around the globe.