Further integration of the money market over time shifted the focus of policy from twelve regional discount policies to a single national policy. In addition, concern about operational efficiencies and about the level of borrowing led to a move from discount rates to open market operations as the policy instrument of choice.
This shift may also have been aided by the expansion of the government bond market during and after World War I. The use of open market operations accelerated the desire for coordination of policy at the national level, so that one Reserve Bank was not draining liquidity at the same time that another was adding liquidity.