However, nothing prevents a central bank from switching its focus from the price of reserves to the quantity or growth of reserves. When  BIS Review 3/2004  3  stated in terms of quantities, it becomes apparent that even if the price of reserves (the federal funds rate) becomes pinned at zero, the central bank can still expand the quantity of reserves.
That is, reserves can be increased beyond the level required to hold the overnight rate at zero--a policy sometimes referred to as “quantitative easing.” Some evidence exists that quantitative easing can stimulate the economy even when interest rates are near zero; see, for example, Christina Romer’s (1992) discussion of the effects of increases in the money supply during the Great Depression in the United States.