Julia Giese, Michael McLeay, David Aikman and Sujit Kapadia

Central banks have been using a range of monetary policy and macroprudential tools to maintain monetary and financial stability. But when should monetary versus macroprudential tools be used and how should they be combined? Our recent paper develops a macroeconomic model to answer these questions. We find that two instruments are better than one. Used alone, interest rates can control inflation, but are ineffective for financial stability. Policymakers can do better by also deploying the countercyclical capital buffer, a tool that varies the amount of additional capital banks must set aside. The appropriate combination of tools can vary: both should tighten to counter a joint expansion of credit and activity, but move in opposite directions during an exuberance-driven credit boom.