The second challenge relates to the unintended side effects of monetary policy. https://www.ecb.europa.eu/press/key/date/2020/html/ecb.sp201124~bcaebee7c0.en.html  10/13  24/11/2020  COVID-19 and monetary policy: Reinforcing prevailing challenges  The wide-ranging nature of the instruments we use today raises the bar of accountability. But side effects are a difficult topic for central banks, no less than for medical practitioners.
During the years of economic expansion, strong domestic demand was the main driving force behind economic growth, with domestic demand itself being fuelled by, among other things, rapid increases in real disposable income, and overly optimistic expectations about future income.