How far to go – and to remain – in the direction of highly expansionary monetary policy hinges on the
balance of marginal benefits and costs of additional monetary easing and its expected evolution over time.
This paper sketches a framework for assessing this balance and applies it to four OECD economic areas:
the euro area, Japan, the United Kingdom and the United States. The effectiveness of further stimulus via
quantitative easing or forward guidance in affecting asset prices, interest rates and credit flows will depend
on the state of the economy and the functioning of financial markets. Marginal costs could rise due to
excessive risk-taking; higher inflation expectations; higher likelihood of ever-greening; and higher risks of
financial instability in the exit phase, especially when exit from monetary accommodation is close in time
and signs of negative effects are already apparent. The balance of marginal benefits and costs is found to
be different across the main OECD areas. In the United States, the case for additional stimulus is
weakening, while the opposite is true for the euro area and Japan. In the United Kingdom, the assessment
is less clear cut.
