What has been unconventional over recent times is the  way these tools have been used. Negative interest rates The first of the four tools discussed in the report is negative policy rates. This is one tool that is truly unconventional.
Prior to the financial crisis, it was widely thought that zero was the lower bound for the policy interest rate – so it was common to talk about the ‘ZLB’, or the zero lower bound. It was thought that if interest rates went below zero, people would hold their savings in banknotes rather than be charged by their bank to deposit their money.