In contrast, experience using the balance sheet as an active tool has been very limited and largely confined to a highly unusual period around the Global Financial Crisis, when short-term interest rates were constrained by the zero lower bound.
Predictability, parsimony, precision, and clarity of communications all would seem to argue in favor of focusing policy on a single active tool that is most familiar. In short, it makes sense to focus policy on the tool whose effects are better understood by both policymakers and the public in circumstances where the tools are largely substitutes for one another.