Central bank and government have been in direct control of money supply for the last 2 decades. Your understanding seems to be glaring missing on that. Whatever econ textbook you have been reading or learning from must be written pre-Clinton time. Just look at how much Americam Treasury pumping money in from direct Fed purchases of T-bills (printing money via phone calls internally or else Jerome will get retaliated by FBI). The situation over BOJ is even worst as they have been doing this internal phone call and then print in the last 3 decades. Check their debt vsd gdp! If private banking can print money on their own, why would they bother with centralized interest rate announcement? Just print and people will flock to it instead of Jerome!