The precise motivations for these asset purchase programs varied across countries, but a common motivation was to lower risk-free interest rates out along the term spectrum, well beyond the shortterm policy rate. Buying government bonds was seen as reinforcing policy rate cuts and/or acting as a substitute for further reductions in the policy rate once it was at its lower bound.
Ref #7076865 v2.1  11  to reverse in the aftermath of the GFC, due to the fiscal stimulus provided during the recession and following the Canterbury earthquakes in 2010/11.