In the current downturn, however, the Federal Reserve has faced two historically unusual constraints on policy. First, the financial crisis, by increasing credit risk spreads and inhibiting normal flows of financing and credit extension, has likely reduced the degree of monetary accommodation associated with any given level of the federal funds rate target, perhaps significantly.
Second, since December, the targeted funds rate has been effectively at its zero lower bound (more precisely, in a range between 0 and 25 basis points), eliminating the possibility of further stimulating the economy through cuts in the target rate.