Analysis suggested that the effective bound on interest rates was lower than previously thought and that sovereign purchases could have a substantial impact via banks, because they would reduce financing costs for banks, and encourage them to lend to the real economy rather than invest in sovereign bonds. The latest estimates bear this out.
The policy package is found to have had a substantial impact, contributing 2.7 percentage points to euro area real GDP growth between 2015 and 2018 and 1.3 percentage points to inflation.