Quantitative easing is distinguished from standard central banking monetary policies, which are usually enacted by buying or selling government bonds on the open market to reach a desired target for the interbank interest rate. However, if a recession or depression continues even when a central bank has lowered interest rates to nearly zero, the central bank can no longer lower interest rates. The central bank may then implement a set of tactics known as quantitative easing. This policy is often considered a last resort to stimulate the economy.[22][23]
A central bank enacts quantitative easing by purchasing—without reference to the interest rate—a set quantity of bonds or other financial assets on financial markets from private financial institutions.[8][24] The goal of this policy is to facilitate an expansion of private bank lending; if private banks increase lending, it would increase the money supply. Additionally, if the central bank also purchases financial instruments that are riskier than government bonds, it can also lower the interest yield of those assets.
Quantitative easing, and monetary policy in general, can only be carried out if the central bank controls the currency used in the country. The central banks of countries in the Eurozone, for example, cannot unilaterally expand their money supply and thus cannot employ quantitative easing. They must instead rely on the European Central Bank (ECB) to enact monetary policy.