An important issue is the ‘chicken and egg’ syndrome again, where market participants have been reluctant to trade futures until liquidity has improved, but liquidity will not improve until more participants enter the market and trade.
As William Poole has shown, if spending shocks predominate, it makes sense to target money, or monetary quantities; if money demand shocks predominate, it makes sense to target interest rates. In the short run, money demand shocks do seem to predominate, and most central banks in the world now operate in terms of some short-term interest rate.